PACKAGING CORPORATION OF AMERICA

March 23, 201828, 2024

Dear PCA Stockholder:

You are cordially invited to attend the 20182024 Annual Meeting of Stockholders to be held at our corporate office, located at 1955 West1 N. Field Court, Lake Forest, Illinois, on Tuesday,Wednesday, May 15, 20188, 2024 at 8:30 a.m., central time.

Following this page is the formal notice of the meeting and our Proxy Statement. Also enclosed is a proxy or voting instruction card, a postage-paid envelope and our 20172023 Annual Report to Stockholders.

It is important that your shares are represented at the meeting. You may vote over the Internet or by mailing a proxy or voting instruction card. Whether or not you expect to attend the meeting, please vote your shares by following the voting instructions on the enclosedyour notice of availability of proxy materials or your proxy or voting instruction card.

Sincerely,

Mark W. Kowlzan Chairman and Chief Executive Officer

PACKAGING CORPORATION OF AMERICA

1955 West1 N. Field Court

Lake Forest, Illinois 60045

(847)482-3000

TABLE OF CONTENTS

PACKAGING CORPORATION OF AMERICA

1955 West1 N. Field Court

Lake Forest, Illinois 60045

(847)482-3000

Please note that if you hold your shares in “street name” (that is, through a broker or other nominee), you will need to bring a copy of your voting instruction card or a brokerage statement reflecting your stock ownership as of the record date and check in at the registration desk at the meeting.

What constitutes a quorum?

A quorum is necessary to hold a valid meeting. The presence at the meeting, in person or by proxy, of the holders of a majority of our outstanding common stock on the record date will constitute a quorum for our meeting. Brokernon-votes and proxies received but marked as abstentions will be included as present for purposes of establishing a quorum. A brokernon-vote occurs when a nominee holding shares for a beneficial owner does not vote on a particular proposal because the nominee does not have discretionary voting power for the particular matter and has not received voting instructions from the beneficial owner. We expect that nominees will not have discretionary authority for Items 1 (Election of Directors) and, 3 (Approval of Second Amended and Restated 1999 Long-Term Equity Incentive Plan), 4 (Approval of Executive Compensation), and 5 (Shareholder Proposal Regarding Director Resignations) and will have discretionary authority for Item 2 (Ratification of Independent Registered Public Accounting Firm).

If a quorum is not present at the annual meeting, the stockholders present may adjourn the annual meeting from time to time, without notice, other than by announcement at the meeting, until a quorum is present or represented. At any such adjourned meeting at which a quorum is present or represented, any business may be transacted that might have been transacted at the original meeting.

Why did I receive notice in the mail regarding the Internet availability of proxy materials instead of a full set of proxy materials?

The Securities and Exchange Commission (SEC) permits us to furnish proxy materials by providing access to those documents on the Internet. Stockholders will not receive printed copies of the proxy materials unless they request them. The notice instructs you as to how to submit your proxy on the Internet. If you would like to receive a paper or email copy of the proxy materials, you should follow the instructions in the notice for requesting those materials.

How do I vote if shares are held in my name?

If the shares of our common stock are held in your name, you may vote on matters to come before the meeting in two ways:

Your shares will be voted as you indicate. If you return thea proxy card but you do not indicate your voting preferences, then the proxies named on the proxy card will vote your sharesforall of the directors nominated, andforapproval of the other items before the meeting.Items 2 through 4 and against Item 5. Should any other matter requiring a vote of stockholders arise, the stockholders confer upon the proxies discretionary authority to vote the shares represented by such proxy on any such other matter in accordance with their best judgment. All of the proxies are our officers.

How do I vote if I hold my shares through a broker, bank or other nominee?

Stockholders whose shares of our common stock are held in street name must either direct the record holder of their shares as to how to vote their shares of our common stock or obtain a proxy from the

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record holder to vote at the meeting. These stockholders should check the voting instruction cards used by their brokers or nominees for specific instructions on methods of voting, including by telephone or using the Internet.

How do I vote shares I hold in the 401(k) plan?

If you are one of our employees who holds common stock through the PCA Employee Stock Ownership Plan (which holds the PCA common stockCommon Stock Fund in both the Packaging Corporation of America Retirement Savings Plan for Salaried Employees the PCA Common Stock Fund inand the Packaging Corporation of America Thrift Plan for Hourly Employees and the PCA Common Stock Fund in the Boise Paper Holdings, L.L.C. Retirement Savings Plan)Employees), you will receive from the plan trustee a request for voting instructions with respect to the shares of our common stock representing your proportionate interest in the plans. You are entitled to direct the plan trustee how to vote your proportionate interest of shares in those plans.

What happens if a nominee for director does not receive a majority of the vote in an uncontested election?

AllTen of the eleven nominees for election to the electionboard of directors at the 20182024 annual meeting are incumbent directors currently serving on the board and the election is uncontested. Ms. Gowland is being nominated for election for the first time. An incumbent director nominee who does not receive the necessary number of votes to be elected at the annual meeting would, under Delaware law, continue to serve on the board as a “holdover director.” However, under our bylaws, any director who fails to receive the necessary number of votes to be elected must tender his or her resignation to the board promptly. Our independent directors (excluding the director who tendered the resignation) would be required to determine whether to accept or reject the resignation, or whether to take any other action. The board would then act on the tendered resignation and publicly disclose its decision within 90 days following certification of the stockholder vote. If Ms. Gowland does not receive a majority of the vote, she will not be elected to the board.

Who will be tabulating and certifying votes at the meeting?

We have engaged Computershare Trust Company, N.A., our transfer agent, to serve as the tabulator of votes and a representative of Computershare to serve as inspector of election and certify the votes.

ELECTION OF DIRECTORS

ITEM NO. 1 ON PROXY CARD

Our board currently has ten directors. Effective upon the time of directors has eleven members, allthe 2024 annual meeting, the size of whom are elected annually.the board will be increased to 11 directors. The eleven11 nominees named below are proposed to be elected at thisthe annual meeting to serve until the 20192025 Annual Meeting of Stockholders and until their successors are elected and qualified. All of the nominees have been nominated for election by our board of directors upon the recommendation of the nominating and governance committee of the board of directors.

A properly submitted proxy will be voted by the persons named on the proxy card for the election of each nominee, unless you vote against the nominee or abstain. If elected, each nominee will serve until the expiration of his or her term and his or her successor is elected and qualified or until his or her earlier resignation, removal or death. Each of the nominees is willing to serve if elected, and the board of directors has no reason to believe that any of the nominees will be unavailable for election. If such a situation should arise, the proxy will be voted in accordance with the best judgment of the proxy holder for such person or persons as may be designated by the board of directors, unless the stockholder has directed otherwise.

Set forth below is information regarding each nominee. Standing for election are:

Mark W. Kowlzan is 6369 years old and has served as Chief Executive Officer and a director of PCA since July 2010 and as Chairman since January 2016. From 1998 through June 2010, Mr. Kowlzan led PCA’s containerboard mill system, first as Vice President and General Manager and then as Senior Vice President —Containerboard.President—Containerboard. From 1996 through 1998, Mr. Kowlzan served in various senior operating positions with PCA in its mill operations, including as manager of the Counce, Tennessee linerboard mill. Prior to joining PCA, Mr. Kowlzan spent 15 years at International Paper Company, where he held a series of operational and managerial positions within its mill organization. Mr. Kowlzan has been a member of the board of directors of American Forest & Paper Association since February 2011. Mr. Kowlzan was chosen to serve on our board primarily for his extensive leadership and technical expertise in the paper and packaging industries and his familiarity with our business through his leadership of our containerboard mill system and our company. Mr. Kowlzan self identifies as a Caucasian male.

Cheryl K. Beebeis 6268 years old and has served as a director of PCA since May 2008. From February 2004 until her retirement in February 2014, Ms. Beebe served as the Chief Financial Officer of Ingredion Incorporated (formerly named Corn Products International, Inc.), a manufacturer and seller of a number of ingredients to food and industrial customers, including as Executive Vice President beginning in 2010.customers. Ms. Beebe previously served Ingredion as Vice President, Finance from July 2002 to February 2004, as Vice President from February 1999 to 2004 and as Treasurer from 1997 to February 2004. She served as Director of Finance and Planning for CPC International Inc.’s (now named Unilever BestFoods) Corn Refining Business from 1995 to 1997 and as Director of Financial Analysis and Planning for its Corn Products North America business from 1993 to 1995. From 1980 to 1993,1997, she served in various financial positions in CPC’s U.S. consumer food business, North American audit group and worldwide corporate treasury function.of increasing responsibility for Corn Products. Ms. Beebe is a member of the board of directors of The Mosaic Company and served on the boards of directors of Convergys Corporation.Corporation and Hanesbrands, Inc. during the past five years. Ms. Beebe is a trustee of Goldman Sachs Asset Management funds. Ms. Beebe was chosen to serve on our board primarily for her experience as a chief financial officer of a public company, her extensive financial and accounting background, and her knowledge of the manufacturing industry and the strategic and business issues and risks similar to those facing PCA. Ms. Beebe self identifies as a Caucasian female.

Duane C. Farringtonis 5965 years old and has served as a director of PCA since August 2015. Mr. Farrington has beenwas employed by State Farm Mutual Automobile Insurance Company sincefrom 1980 servinguntil his retirement in 2020. He served State Farm as Senior Vice President for Sales and Operations in theirthe mid-Atlantic operation from 2005 to 2008. He moved to theirthe corporate headquarters in 2009 and was named Executive Vice President and Chief Administrative Officer in 2013.2013 and served in such position until he retired in 2020. In his State Farm senior leadership role, he hashad overall responsibility for the

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organization’s information technology, systems and business integration, information security, and innovation functions. Mr. Farrington earned the Chartered Property Casualty Underwriter (CPCU) designation in 1995. Mr. Farrington was chosen to

working with and assisting similarly situated companies to ours, his extensive financial, auditing and accounting background and his knowledge of both thesimilarly situated manufacturing industry and PCA.companies. Mr. Maurer self identifies as a Caucasian male.

Samuel M. Mencoffis 6167 years old and has served as a director of PCA since January 1999 and served as Vice President of PCA from January 1999 through January 2000. Mr. Mencoff has been employed principally by Madison Dearborn Partners, LLC since 1993 and currently serves as Senior Advisor, after having served as Co-Chief Executive Officer.Officer from 2008 to 2023. From 1987 until 1993, Mr. Mencoff served as Vice President of First Chicago Venture Capital. Mr. Mencoff has served on the board of Boise Cascade Company during the past five years. Mr. Mencoff was chosen to serve on our board primarily for his substantial operational and financial experience gained from the acquisition and management of similarly-situated portfolio companies as managing director andCo-Chief Executive Officer ofduring his career at Madison Dearborn. Mr. Mencoff self identifies as a Caucasian male.

Roger B. Porteris 7177 years old and has served as a director of PCA since May 2005. Mr. Porter is currently the IBM Professor of Business and Government at Harvard University and has served on the faculty at Harvard University since 1977. Mr. Porter also held senior economic policy positions in the Gerald Ford, Ronald Reagan and George H.W. Bush White Houses, serving as special assistant to the President and executive secretary of the Economic Policy board from 1974 to 1977, as deputy assistant to the President and director of the White House Office of Policy Development from 1981 to 1985, and as assistant to the President for economic and domestic policy from 1989 to 1993. Mr. Porter is also a director of TennecoExtra Space Storage Inc., and has served as a director of Zions Bancorporation and Extra Space StorageTenneco, Inc. during the last five years. Mr. Porter was chosen to serve on our board primarily for his perspectives and insights gained through his significant business, governmental and public policy experience.

Determination of Director Independence

Our corporate governance guidelines provide that a majority of the board of directors willshall consist of independent directors. All of our directors other than Mark W. Kowlzan, our chairmanChairman and chief executive officer,Chief Executive Officer, and Paul T. Stecko, our former chairmanChairman and Chief Executive Officer who served as an executive officer from 1999 to 2013 and in an advisory capacity through the end of 2017, are independent and not employed by us. In determining independence of those directors, the nominating and governance committee conducts an annual review and reports its findings to the full board. The nominating and governance committee determines if any material relationships exist that would impair the independence of any of thenon-employee directors and makes a recommendation to the board as to the independence of the directors.

A director may not qualify as independent unless the board of directors affirmatively determines that the director has no material relationship with us. The board of directors has not adopted categorical standards of materiality for independence purposes (other than those set forth in the New York Stock Exchange (“NYSE”) listing standards). In connection with the review performed at its February 27, 201828, 2024, meeting, the committee and the board were not aware of any relationship that would disqualify anon-employeeany nominee for director, other than Mr. Kowlzan, our current Chief Executive Officer, and Mr. Stecko, our former Chief Executive Officer, from being independent. The board and the nominating and governance committee considered the following relationships in making its determination.determination:

Madison Dearborn Partners, which employs Mr. MencoffSouleles asco-Chief Co-Chief Executive Officer, and Mr. Souleles as Managing Director, is a private equity firm that has investments in companies that may purchase products or services from, or provide products and services to, us in the ordinary course of business in amounts that are not material in amount or significance. Mr. Mencoff and Mr. Souleles areis not compensated directly or indirectly as a result of any such transactions, dodoes not otherwise have an interest in such transactions and areis not involved in any manner in such transactions. Accordingly, we do not consider any such transactions to impair theirhis independence. As Mr. MencoffSouleles may be deemed to beneficially own more than 10% of certain portfolio companies, we report certain of these transactions under “Transactions with Related Persons” elsewhere in this proxy statement. Mr. Mencoff serves as Senior Advisor to Madison Dearborn, which is a non-executive position, after having served as Co-Chief Executive Officer through May 2023.

We purchase services in the ordinary course of business from GATX Corporation, which currently employs Mr. Lyons as President and Chief Executive Officer. The amount of 2023 purchases was approximately $355,200, which is less than 0.1% of the 2023 sales of each of GATX and PCA. Mr. Lyons is not directly involved in, and is not compensated as a result of, this business relationship. Accordingly, the board determined that this business relationship was not a material relationship between Mr. Lyons and PCA, and determined him to be independent and eligible to serve on the audit committee.

Ms. Gowland was employed by Boise, Inc. prior to her retirement in March 2014. We acquired Boise Inc. in October 2013. Between the time of the acquisition and her retirement, she served in a non-executive position, after having served as Senior Vice President, General Counsel and Secretary of Boise. She does not receive any compensation from us other than pension and retirement benefits. Due to the substantial length of time since her employment with Boise, that she did not serve in an executive capacity after we acquired Boise and that she has only received retirement benefits that are not contingent on present or future service, the board determined that she does not have a material relationship with us and will serve as an independent director.

Based on the report and recommendation of the nominating and governance committee, the board of directors has determined that the following directors and nominees, which constitute nine of the eleven11 nominees for election to the board, are independent: Cheryl K. Beebe, Duane C. Farrington, Hasan Jameel,

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Karen E. Gowland (upon her election to the board), Donna A. Harman, Robert C. Lyons, Thomas P. Maurer, Samuel M. Mencoff, Roger B. Porter and Thomas S. Souleles and James D. Woodrum.Souleles.

20172023 Board of Directors Meetings

The board met eightfour times during 2017.2023. All nominees for election at the 20182024 annual meeting attended allat least 75% of the meetings of the board and the committees on which he or she was a member held during the year. All of our directors attended the 20172023 Annual Meeting of Stockholders, and all of our directors are expected to attend the 20182024 Annual Meeting of Stockholders.

Leadership Structure

Effective January 1, 2016, the board determined to combine the roles of Chairman and Chief Executive Officer because of the efficiency and effectiveness of board conduct and proceedings gained from Mr. Kowlzan’s familiarity with our operations as a result of serving as chief executive officer and a director, enabling the board to focus on the most relevant decisions, issues and risks involving the company. As the company’s strategy focuses on operational excellence and capital allocation to further such operational excellence, the board believes that familiarity with company operations is important to board leadership, which is achieved under the current leadership structures.

To help maintain a strong and appropriate independent director presence, the independent members of the board have elected Mr. Mencoff as the “lead director.” The lead director is an independent director elected by the independent directors on the board. In addition to presiding at executive sessions of independent directors, the

Board Committees

The board has standing nominating and governance, compensation, audit and auditsustainability committees. As required under NYSE rules and the committee charters, each of thesethe nominating and governance, compensation and audit committees consists solely of independent directors. Additional committee service eligibility requirements for audit committee members and compensation committee members are set forth in the committee charters and described below.

Nominating and Governance Committee

Mr. Porter (Chair), Mr. Mencoff, Mr. Souleles and Mr. WoodrumSouleles serve on the nominating and governance committee. The nominating and governance committee met twofour times during 2017.2023. Ms. Gowland will join the committee upon her election to the board.

The nominating and governance committee’s primary responsibilities include, among other things:

The committee leads our board recruiting and nominating efforts. As the committee believes that the sizeefforts, as well as annual performance evaluations of the board, is appropriate, we have not recruited new directors since 2015. its committees and its members. Areas covered include quality of information provided to the board, the quality of interaction between the board and management, the frequency of meetings of the board and the overall effectiveness of board proceedings, conduct and leadership.

The nominating and governance committee seeks to identify as candidates for director persons from various backgrounds, with a variety of life experiences, with a reputation for integrity and good business judgment, and who have experience in highly responsible positions in professions or industries relevant to the conduct of our business. In selecting potential new candidates, the committee will take into account the current composition of the board and the extent to which a candidate’s particular expertise and experience will complement the expertise and experience of other directors.

The committee also considers diversitydoes not target a specified percentage of gender or racially diverse members, but does consider the gender and racially diverse makeup of the board as a factor in seeking new candidates and recruited and elected one ethnicallyendeavors to include racially or gender diverse candidatecandidates in the lastpool of available candidates in any director search. The committee also takes into account the expectations of stockholders in terms of the gender and racial composition of the board and prioritized recruiting a female director, in part due to shareholder feedback in 2023 regarding gender diversity. The three years, such candidate beingmost recent new nominees to join the only new director elected to PCA’s board in that time period.are gender and/or racially diverse. The committee believes that the diversity that exists in the board composition is a benefit to PCA, and, in accordance with its recruitment policy, will continue efforts to recruit candidates from a pool that includes qualified diverse candidates.candidates when openings on the board exist. The committee’s policy is to include gender or racially diverse candidates in the pool of candidates when searching for a new director.

Among other things, the primary skills and experience sought by the committee and the board include relevant leadership or technical experience in the paper packaging and manufacturingpackaging sectors, expertise in capital allocation and decision making, senior leadership experience in complex business environments, sustainability experience, governance andor public policy expertiseexperience and expertiseexperience in finance, auditing and accounting and information technology.technology systems and security experience. Multiple board members possess each of these attributes. Accordingly, the committee believes that the board as currently composed adequately satisfiesnominees collectively satisfy the objectives described above, and recommended the nomination of each member for an additional term.term and recommended the nomination of Ms. Gowland for election to the board.

The table below lists the skills and experience gained through prior business experience that we consider important in light of our current business strategy and structure and the self-identified gender and race of each director nominee by EEO-1 Classification:

Skill/Experience

Leadership or Technical Experience in the Paper / Packaging Sectors

X

X

X

X

Expertise in Capital Allocation and Decision Making

X

X

X

X

X

X

X

Senior Leadership Experience in Complex Business Environments

X

X

X

X

X

X

X

X

X

X

X

Sustainability Experience

X

X

X

Governance or Public Policy Experience

X

X

X

Finance, Auditing and Accounting Experience

X

X

X

X

X

Information Technology Systems and Security Experience

X

X

X

X

Gender

Male

X

X

X

X

X

X

X

X

Female

X

X

X

Race/Ethnicity

White

X

X

X

X

X

X

X

X

X

X

Hispanic

Black or African American

X

Asian

Native Hawaiian or other Pacific Islander

American Indian or Alaska Native

Two or more races

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We have not established term limits or a mandatory retirement age from our board.board and we believe that the tenure of our board benefits our company and our shareholders. As our board is focused on our strategic goal of operational excellence and capital allocation in furtherance of more efficient and productive operations and customer service, it is important for board members to have a high degree of familiarity with our operations. We believe that experience gained from board service promotes this objective and has helped lead to a well-functioning and highly performing board.board, driving strong company performance that generates shareholder value, with PCA’s total stockholder return more than doubling the return of the S&P 500 over the median tenure of our board members. The median tenure of our board members is nine14 years.

The committee leads annual performance evaluations of the board, its committees and its members. Areas covered include quality of information provided to the board, the quality of interaction between the board and management, the frequency of meetings of the board and the overall effectiveness of board proceedings, conduct and leadership.

For more information on consideration of nominees for our board, see “Other Information —RecommendationsInformation—Recommendations for Board Nominated Director Nominees.” The written charter of the nominating and governance committee is available on PCA’s website atwww.packagingcorp.comunder the section Investor RelationsInvestors — Corporate Governance.

Compensation Committee

Mr. WoodrumSouleles (Chair), Mr. Mencoff, Mr. Porter and Mr. SoulelesPorter serve on the compensation committee. Ms. Gowland will join the committee upon her election to the board. Each member of the compensation committee must satisfy all independence standards applicable to compensation committee members as set forth in the rules of the SEC and the listing standards of the New York Stock Exchange. The committee must have two members that qualify as“non-employee “non-employee directors” pursuant to SEC Rule16b-3 and “outside directors” for purposes of Section 162(m) of the Internal Revenue Code of 1986, as amended (“Code Section 162(m)”). 16b-3. As composed, the committee satisfies these standards. The committee met sixfive times during 2017.2023.

The compensation committee’s primary responsibilities include, among other things:

made for the named executive officers, the committee or subcommittee meets in executive session with no members of management present. For compensation matters on which the board acts, the chairman of the committee reports the committee’s recommendations on executive compensation to the board. Independent advisors and the human resources department support the committee and the subcommittee in their duties and may be delegated authority to fulfill certain administrative duties regarding the compensation programs. The committee has authority under its charter to retain, approve fees for and terminate advisors, consultants and agents, as it deems necessary to assist in the fulfillment of its responsibilities. Before engaging compensation consultants, independent legal counsel and other compensation advisors, the committee will assess the independence of any such persons, taking into consideration all factors relevant to that person’s independence from management.

Compensation Committee Interlocks and Insider Participation.Participation

The compensation committee is composed of directors who are not our employees and have not beenserved as our employees.officer. None of our executive officers servesserve as a member of the board of directors or compensation committee of any entity that has one or more executive officers serving on our board or compensation committee.

Madison Dearborn Partners, which employs Mr. MencoffSouleles asco-Chief Co-Chief Executive Officer, and Mr. Souleles as Managing Director, is a private equity firm that investshas investments in companies that may purchase products or services from, or sellprovide products and services to, us in the ordinary course of business in amounts that are not material in amount or significance. Mr. Mencoff andAs Mr. Souleles are not compensated directly or indirectly as a result of any such transactions, do not otherwise have an interest in such transactions and are not involved in any manner in such transactions. Mr. Mencoff may be deemed to beneficially own more than 10% of certain portfolio companies. Transactions during 2017 involvingcompanies, we report certain of these transactions under “Transactions with Related Persons” elsewhere in this proxy statement. Mr. Mencoff serves as Senior Advisor to Madison Dearborn, portfolio companies to which we sold, or from which we purchased, more than $120,000 of products or services are describedis a non-executive position, after having served as follows:Co-Chief Executive Officer through May 2023.

Audit Committee

Ms. Beebe (Chair), Mr. Farrington, Dr. Jameel,Ms. Harman, Mr. Lyons and Mr. Maurer serve on the audit committee. Each member of the audit committee must be financially literate as required under the NYSE listing standards and meet the heightened independence standards required for audit committee members under SEC rules and the NYSE listing standards. All committee members were determined to satisfy these standards. The board of directors has determined that each of Ms. Beebe, Mr. Lyons and Mr. Maurer is an “audit committee financial expert” within the meaning of SEC rules. The committee met tennine times during 2017.2023.

The written charter of the audit committee is available on our website atwww.packagingcorp.comunder the section Investor RelationsInvestors — Corporate Governance.

Sustainability Committee

Ms. Harman (chair), Mr. Farrington, Mr. Kowlzan, and Mr. Porter serve on the sustainability committee. The sustainability committee met four times during 2023. The sustainability committee’s primary responsibilities include, among other things:

The written charter of the sustainability committee is available on our website at www.packagingcorp.com under the section Investors — Corporate Governance.

Communication with the Board of Directors

Interested parties, including stockholders, may communicate directly with the lead director, the chairman of the audit committee, the board of directors or the independent directors as a group by writing to those individuals or the group at the following address: c/o Kent A. Pflederer, Corporate Secretary, Packaging Corporation of America, 1955 West1 N. Field Court, Lake Forest, IL 60045. Correspondence will be forwarded to the appropriate person or persons. When reporting a concern, please supply sufficient information so that the matter may be addressed properly. Although you are encouraged to identify yourself to assist us in effectively addressing your concern, you may choose to remain anonymous, and we will use our reasonable efforts to protect your identity to the extent appropriate or permitted by law. In addition, employees may communicate confidentially any concerns related to our accounting, internal accounting controls or auditing matters, business principles or policies, or suspected violations, by calling the toll-free help line established by us. The toll-free help line is monitored bynon-PCA personnel and all calls are communicated to our corporate security department. Any complaints regarding accounting, internal controls or auditing matters are forwarded directly to the chairman of the audit committee and the chief financial officer.

Code of Ethics

All of our employees, including all officers, are required to abide by our long-standing StatementCode of Ethics and Business Principles.Conduct. Also, separate Codes of Ethics for our executive officers and principal accounting personnel, as well as our directors, are in place to help ensure that our business is conducted in a consistently legal and ethical manner. These documents cover all areas of professional conduct, including employment policies, conflicts of interest, fair dealing and the protection of confidential information, as well as strict adherence to all laws and regulations applicable to the conduct of our business. We conduct regular training on the Code for our officers and employees. The full text of our StatementCode of Ethics and Business PrinciplesConduct and the Codes of Ethics are published on our website atwww.packagingcorp.comunder the section Investor RelationsInvestors — Corporate Governance.

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We will disclose future amendments to, or waivers from, certain provisions of these Codes of Ethics for executive officers and directors on our website within four business days following the date of such amendment or waiver, if they occur.

RATIFICATION OF APPOINTMENT OF THE INDEPENDENT REGISTERED PUBLIC

ACCOUNTING FIRM

ITEM NO. 2 ON PROXY CARD

The audit committee has appointed KPMG LLP as the independent registered public accounting firm to serve as our auditors for the year ending December 31, 2018,2024, and has further directed that we submit the selection of the independent registered public accounting firm for ratification by the stockholders at the annual meeting. Representatives of KPMG LLP are expected to be present at the meeting. They will have the opportunity to make a statement if they wish to do so and will be available to respond to appropriate questions.

Stockholder Ratification

We are not required to submit the appointment of KPMG LLP for ratification by our stockholders. However, we are doing so as a matter of good corporate practice. If the stockholders do not ratify the appointment, the audit committee will reconsider whether or not to retain that firm. Even if the selection is ratified, the audit committee in its discretion may direct the appointment of a different independent registered public accounting firm at any time during the year if the committee determines that such an appointment would be in our best interests and that of our stockholders.

The board of directors, based upon the recommendation of the audit committee, unanimously

recommends a voteFORthe ratification of the appointment of KPMG LLP as the

independent registered public accounting firm to serve as PCA’s auditors for 2018.2024.

Fees to the Independent Registered Public Accounting Firm

Audit Fees.Fees to KPMG LLP for audit services totaled approximately $3,449,000$3,556,000 for 20172022 and $3,232,000$3,849,500 for 20162023, including, fees associated with the annual audit (including internal control reporting), reviews of our quarterly reports on Form10-Q and accounting consultations, and, in 2023, fees associated with a registered public offering of debt securities, including delivery of a comfort letter relating to a registered public offering.the underwriters.

Audit-Related Fees.Fees to KPMG LLP for audit-related services totaled approximately $208,000$16,000 for 20172022 and $188,400$16,000 for 2016.2023. Audit-related services principally include benefit plan audits and other services reasonably related to the audit.audit in both years.

Tax Fees.Tax fees include fees for tax compliance, tax advice and tax planning services. We did not pay any tax fees to KPMG LLP in 20172022 or 2016.2023.

All Other Fees.We did not pay any other audit related fees to KPMG LLP in 20172022 or 2016.2023.

Audit CommitteePre-Approval Policy for Audit andNon-Audit Services. Services

Pursuant to its written charter, the audit committee is responsible for adopting, and has adopted, a policy topre-approve all audit and permittednon-audit services to be performed for us by the independent registered public accounting firm. Prior to engagement of the independent registered public accounting firm for the next year’s audit, we or the independent registered public accounting firm submit to the committee for approval an aggregate request of services expected to be rendered during that year for each of the four categories of services outlined above. Prior to engagement, the committeepre-approves these services by category of service. The fees are budgeted and the committee requires the independent registered public accounting firm and us to report actual fees versus the budget periodically throughout the year by category of service. During the year, circumstances may arise when it may become necessary to engage the independent registered public accounting firm for additional services not contemplated in the originalpre-approval. In those

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instances, the audit committee

PROPOSAL ON EXECUTIVE COMPENSATIONAPPROVAL OF THE SECOND AMENDED AND RESTATED 1999 LONG-TERM EQUITY INCENTIVE PLAN

ITEM NO. 3 ON PROXY CARD

On February 28, 2024, our board of directors approved the amendment and restatement of the Second Amended and Restated 1999 Long-Term Equity Incentive Plan (the “Plan”), subject to stockholder approval at the 2024 annual meeting. The board has long believed that awards under the Plan provide appropriate incentives to PCA officers, directors and employees to maximize stockholder value and otherwise contribute to the success of PCA. The amendment and restatement of the plan will allow PCA to continue to grant equity and equity-based awards.

The board has determined that it would be desirable to extend the term of the Plan to the tenth anniversary of the date that the amendment and restatement is approved by the stockholders (the “Effective Date”). Subject to adjustments for changes in capitalization, as of the Effective Date, an aggregate of 3,075,614 shares of common stock may be issued pursuant to the Plan, less one share for every one share granted under the Plan after December 31, 2023 and prior to the Effective Date. The 3,075,614 shares reflects 685,614 shares that remained available for grant under the Plan as of December 31, 2023, plus 2,390,000 newly authorized shares approved by the Company’s stockholders on the Effective Date.

PCA is requesting additional shares in connection with the amendment and restatement of the Plan in order to continue to grant equity and equity-based awards and achieve its overall long term compensation objectives. The Plan was last amended to increase the number of authorized shares on May 2, 2020. Since that time, PCA has made awards of restricted stock and performance units settled in shares of PCA stock. PCA has not awarded stock options since 2007.

In setting and recommending to stockholders the number of additional shares to authorize under the Plan, the board of directors considered the historical number of equity awards granted under the Plan, as well as the company’s three-year average burn rate for the preceding three fiscal years as follows:

Promotion of Good Corporate Governance Practices

The Plan provides for the following:

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Summary of the Plan

A copy of the Plan is attached to this proxy statement as Appendix B. As required, the principal features of the Plan as amended and restated are described below, but such description is qualified in its entirety by reference to the complete text of the Plan. Capitalized terms used in the summary of the Plan that are not otherwise defined have the meanings given to them in the Plan. The amendment and restatement will not become effective unless stockholder approval is obtained at the annual meeting.

General Information

The Plan provides for grants of Non-Qualified Stock Options and Incentive Stock Options (collectively, “Options”), stock appreciation rights (“SARs”) and Full Value Awards (including restricted stock, stock units and performance unit awards). Officers, directors and employees of PCA and its subsidiaries, as well as others who engage in services for PCA or its subsidiaries, are eligible for grants under the Plan. The purpose of the Plan is to provide these individuals with incentives to maximize stockholder value and otherwise contribute to the success of PCA and to enable PCA to attract, retain and reward the best available persons for positions of responsibility.

Shares Available for Issuance Under the Plan; Limitations on Grants

Subject to adjustments for changes in capitalization, as of the Effective Date, an aggregate of 3,075,614 shares of common stock may be issued pursuant to the Plan, less one share for every one share granted under the Plan after December 31, 2023 and prior to the Effective Date.

The following table presents the shares available for future awards (taking into account shares at target level of performance on outstanding performance units), unvested shares of restricted stock and shares issuable pursuant to unvested performance units if paid out at target, as of December 31, 2023, rounded to the nearest thousand shares.

The closing price of the Company’s common stock on the New York Stock Exchange on the record date was $182.91.

If an award under the Plan expires or terminates unexercised, becomes unexercisable or is forfeited, cancelled or otherwise terminates without the issuance of shares, or is settled in cash, the shares subject to the award will again be available for issuance under the Plan. In addition, shares subject to any awards (“Substitute Awards”) that are issued by PCA in assumption of, or in substitution or exchange for, an award previously granted, or the right or obligation to make a future award, in all cases by a company acquired by PCA or any of its subsidiaries or with which PCA or any subsidiary

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combines will not count against the Plan limit or the individual limits on director compensation. The following shares shall not again be made available for issuance under the Plan: (a) shares not issued or delivered as a result of the net settlement of an outstanding Option or SAR, (b) shares used to pay the exercise price or withholding taxes relating to an outstanding award, or (c) shares repurchased on the open market with the proceeds of the exercise price of an Option or SAR.

The maximum number of shares of common stock that may be delivered pursuant to the exercise of Incentive Stock Options under the Plan cannot exceed the Plan limit of 14,340,000.

We may make awards under the Plan to non-employee directors. The value of any awards made to a non-employee director under the plan, together with other compensation payable to such non-employee director, may not exceed $650,000 during any annual period.

The Plan has been in effect since 1999 and is the only equity compensation plan under which shares of PCA common stock have been awarded. In each case, the number of shares (as well as the exercise price of Options and SARs and the individual limit on director compensation) is subject to adjustment in the event of a reorganization, stock split, merger, stock dividend, other asset distribution (other than normal cash dividends) or similar change in the corporate structure of PCA or the outstanding shares of common stock. Shares reserved for issuance under the Plan may be, in whole or in part, authorized and unissued or held as treasury shares.

Subject to adjustments for changes in capitalization, awards granted under the Plan (other than cash-based awards) will vest no earlier than the first anniversary of the date on which the award is granted; provided, that the following awards will not be subject to the foregoing minimum vesting requirement: any (i) Substitute Awards, (ii) shares delivered in lieu of fully vested cash awards, (iii) awards to non-employee directors that vest on the earlier of the one-year anniversary of the date of grant and the next annual meeting of stockholders which is at least 50 weeks after the immediately preceding year’s annual meeting, and (iv) any additional awards up to a maximum of five percent of the total number of shares reserved for issuance under the Plan (including historically); and, provided, further, that the foregoing restriction does not apply to the Committee’s (as defined below) discretion to provide for accelerated exercisability or vesting of any award, including in cases of retirement, death, disability, involuntary termination, or a change in control, in the terms of the award or otherwise.

To the extent provided by the Committee (as defined below), any award under the Plan may be settled in cash rather than shares of stock.

Administration

The Plan is administered by a “Committee” which generally will be the compensation committee of the Board; provided, however that the Committee with respect to awards to non-employee directors will be the full Board. In addition, the Committee will generally be comprised of not fewer than two directors (or a greater number if required for compliance with applicable securities laws) who are independent for purposes of stock exchange listing requirements. The Committee selects award recipients under the Plan, the types of awards to be granted and the applicable terms, conditions, performance criteria, restrictions and other provisions of such awards. The Committee also has the authority to conclusively interpret the Plan. Subject to stock exchange rules, the Committee may delegate all or any portion of its responsibilities or powers under the Plan to persons selected by it.

Eligibility

Directors, officers and employees of PCA and its subsidiaries, as well as other individuals performing significant services for us, or to whom we have extended an offer of employment, will be eligible to

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receive awards under the Plan. However, no award will be effective prior to the date that an eligible individual begins providing services for us and only employees may receive grants of Incentive Stock Options. In each case, the Committee will select the actual participants. As of February 28, 2024, there were approximately ten directors, 11 officers and 550 other employees eligible to participate in the Plan. The Company has a historical practice of not granting awards under the Plan to its consultants and advisors, and at this time does not foresee changing that practice.

Options and SARs

Under the Plan, the Committee may award Incentive Stock Options conforming to the provisions of Code Section 422, Non-Qualified Stock Options which do not conform to the requirements of Code Section 422 and SARs. Incentive Stock Options may only be granted to employees of PCA and its eligible corporate subsidiaries.

The Committee will determine the exercise price of any Option and SAR in its discretion. However, the exercise price of any Option or SAR (other than a Substitute Award) may not be less than 100% of the fair market value of a share of common stock on the date of grant, and the exercise price of an Incentive Stock Option awarded to a person who owns stock constituting more than 10% of PCA’s voting power may not be less than 110% of the fair market value on the date of grant.

Except for adjustments in connection with a corporate transaction or restructuring or reductions approved by PCA’s stockholders, the exercise price of an Option or SAR may not be decreased after the date of grant nor may an outstanding Option or SAR be surrendered to PCA as consideration for the grant of a replacement Option or SAR with a lower exercise price or a Full Value Award. In addition, unless approved by PCA’s stockholders, in no event will any Option or SAR be surrendered to PCA in consideration for a cash payment if, at the time of such surrender, the exercise price of the Option or SAR is greater than the then current fair market value of a share of PCA common stock. PCA may not pay dividends or dividend equivalents on outstanding Options or SARs.

The Committee will determine the terms and conditions of exercise and vesting of each Option and SAR in its discretion. However, the maximum term of an Option or SAR may not exceed ten years from the date of grant or, in the case of an Incentive Stock Option granted to a person who owns stock constituting more than 10% of the PCA’s voting power, five years from the date of grant. In addition, all Options and SARs under the Plan, whether or not then exercisable, generally cease vesting when a participant ceases to be a director, officer or employee of, or to otherwise perform services for, PCA or its subsidiaries and remain exercisable for 90 days after the participant’s termination of employment or service as long as the participant does not engage in competition during that period. The Plan provides, however, that, unless otherwise provided by the Committee, the following special vesting and expiration rules will apply (but in no event will the Option or SAR be exercisable after the expiration of the term):

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The Committee will determine the procedures pursuant to which Options and SARs may be exercised; provided, however, that any SAR will be automatically exercised prior to its expiration date if, upon that date, the fair market value of a share of PCA common stock is greater than the exercise price of the SAR. Upon exercise of the SAR, the participant will receive a number of shares of common stock having a fair market value equal to the difference between the fair market value of a share of common stock on the date of exercise and the exercise price of the SAR multiplied by the number of shares as to which the SAR is exercised. Unless otherwise provided by the Committee, the exercise price of any Option may be paid in any of the following ways (or combination thereof):

Full Value Awards

Under the Plan, the Committee may award “Full Value Awards” which is the grant of one or more shares of PCA common stock or a right to receive one or more shares of PCA common stock in the future (including restricted stock, restricted stock units, deferred stock units, performance stock and performance stock units). Full Value Awards may be subject to certain terms and conditions, including that they may be in consideration of previously performed services or surrender of other compensation, contingent on achievement of performance or other objectives during a specified time (including completion of a period of service), or subject to a substantial risk of forfeiture or other restrictions. The committee may determine other terms and conditions applicable to Full Value Awards, including provisions relating to dividends or dividend equivalents. No dividends or dividend equivalents will be paid or settled on performance-based awards that have not been earned based on the performance criteria and measures established.

The Committee may provide in any Full Value Award provisions relating to a Change in Control, including, acceleration of vesting of, or deemed satisfaction of performance objectives with respect to, the award. If a Full Value Award is continued or substituted with an award determined by the Committee to be substantially equivalent to the original award in connection with a Change in Control, then vesting will be accelerated if the participant’s employment is terminated without cause or for good reason during the two-year period following the change in control. If a substantially equivalent award is not provided in connection with the Change in Control, then the award will immediately vest and be paid out in connection with the Change in Control.

If a Full Value Award is conditioned or paid out upon the achievement of one or more performance objectives, the Committee may: (1) determine the payout or vesting level based upon performance through the date of, or a date before, the Change in Control; and/or (2) determine to pay the award out at the “target” or equivalent level of performance. The Committee may determine that a substantially equivalent award may, after the Change in Control, no longer be subject to achievement of performance objectives and be subject only to continued service through the vesting date set forth in the original Award.

Withholding Taxes and Transferability of All Awards; Notices to Participants

All awards and other payments under the Plan are subject to withholding of all applicable taxes, which withholding obligations may be satisfied, with the consent of the Committee, through the surrender of shares of common stock which the Participant already owns or to which a participant is otherwise

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entitled under the Plan; provided, however, that (1) the amount withheld in the form of shares may not exceed the minimum statutory withholding rate unless elected by the participant; (2) the participant may not elect to have an amount withheld that is less than the minimum statutory withholding rate; and (3) the participant may not elect to have an amount withheld that is more than the maximum statutory withholding rate or such other rate permitted by the Committee that will not result in adverse accounting treatment for PCA. PCA, to the extent permitted or required by law, shall have the right to deduct from any payment of any kind (including salary or bonus) otherwise due to a participant, an amount equal to any federal, state or local taxes of any kind required by law to be withheld with respect to any grant or delivery of shares under the Plan.

Unless the Committee determines otherwise, no award made under the Plan will be transferable other than by will or the laws of descent and distribution or to a participant’s family member by gift or qualified domestic relations order, and each award may be exercised only by the participant, his or her qualified family member transferee, or any of their respective executors, administrators, guardians or legal representatives.

The terms and conditions of each award made under the Plan, including vesting requirements, will be set forth consistent with the Plan in a written (including electronic) notice to the participant.

Amendment and Termination of the Plan and Awards

The Board or the Committee may amend or terminate the Plan at any time and the Committee may amend any award under the Plan; provided, however, that, no amendment or termination may, in the absence of consent to the change by the affected participant (or beneficiary, if applicable), adversely affect the rights of any participant (or beneficiary) under any award granted under the Plan prior to such amendment or termination is adopted. Adjustments pursuant to corporate transactions and restructurings shall not be subject to the foregoing limitations. In addition, the provisions of the Plan relating to repricing of Options and SARs cannot be amended without the approval of PCA’s stockholders and no other amendment will be made to the Plan without the approval of PCA’s stockholders if the approval is required by law or the rules of any stock exchange on which our common stock is listed.

It is our intention that to the extent that any provisions of the Plan or any award under the Plan are subject to Code Section 409A, the Plan and the awards comply with the requirements of Code Section 409A and that the Board will have the authority to amend the Plan as it deems necessary to conform to section 409A. PCA, however, does not guarantee that awards under the Plan will comply with Code Section 409A and the Committee is under no obligation to make any changes to any award to cause such compliance.

Federal Income Tax Consequences

The following is a brief summary of the U.S. federal income tax rules relevant to participants in the Plan, based upon the Code as currently in effect. These rules are highly technical and subject to change in the future, and the discussion does not purport to be a complete description of the tax aspects of the Plan. The following summary relates only to U.S. federal income tax treatment, and the state, local and foreign tax consequences may be substantially different.

Non-Qualified Stock Options. Generally, the grant of a Non-Qualified Stock Option will not result in taxable income to the participant and PCA will not be entitled to a deduction. Except as described below, the participant will realize ordinary income at the time of exercise in an amount equal to the excess of the fair market value of the shares of common stock acquired over the exercise price for those shares of common stock, and PCA will be entitled to a corresponding deduction. Gains or losses

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realized by the participant upon disposition of such shares of common stock will be treated as capital gains and losses, with the basis in such shares of common stock equal to the fair market value of the shares of common stock at the time of exercise.

The exercise of an Non-Qualified Stock Option through the delivery of previously acquired common stock will generally be treated as a non-taxable, like-kind exchange as to the number of shares of common stock surrendered and the identical number of shares of common stock received under the Option. That number of shares of common stock will take the same basis and, for capital gains purposes, the same holding period as the shares of common stock that are given up. The value of the shares of common stock received upon such an exchange that are in excess of the number given up will be includible as ordinary income to the participant at the time of the exercise. The excess shares of common stock will have a new holding period for capital gain purposes and a basis equal to the value of such shares of common stock determined at the time of exercise.

Incentive Stock Options. Generally, the grant of an Incentive Stock Option will not result in taxable income to the participant or a deduction for PCA. The exercise of an Incentive Stock Option will not result in taxable income to the participant or a deduction for PCA provided that the participant was, without a break in service, an employee of PCA and its eligible corporate subsidiaries during the period beginning on the date of the grant of the Option and ending on the date three months prior to the date of exercise (one year prior to the date of exercise if the participant is disabled, as that term is defined in the Code).

The excess of the fair market value of the shares of common stock at the time of the exercise of an Incentive Stock Option over the exercise price is an adjustment that is included in the calculation of the participant’s alternative minimum taxable income for the tax year in which the Incentive Stock Option is exercised. For purposes of determining the participant’s alternative minimum tax liability for the year of disposition of the shares of common stock acquired pursuant to the Incentive Stock Option exercise, the participant will have a basis in those shares of common stock equal to the fair market value of the shares of common stock at the time of exercise.

If the participant does not sell or otherwise dispose of the shares of common stock within two years from the date of the grant of the Incentive Stock Option or within one year after receiving the transfer of such shares of common stock, then, upon disposition of such shares of common stock, any amount realized in excess of the exercise price will be taxed to the participant as capital gain, and PCA will not be entitled to any deduction for Federal income tax purposes. The participant will recognize a capital loss to the extent that the amount realized is less than the exercise price.

If the foregoing holding period requirements are not met, the participant will generally realize ordinary income, and a corresponding deduction will be allowed to PCA, at the time of the disposition of the shares of common stock , in an amount equal to the lesser of (a) the excess of the fair market value of the shares of common stock on the date of exercise over the exercise price, or (b) the excess, if any, of the amount realized upon disposition of the shares of common stock over the exercise price. If the amount realized exceeds the value of the shares of common stock on the date of exercise, any additional amount will be capital gain. If the amount realized is less than the exercise price, the participant will recognize no income, and a capital loss will be recognized equal to the excess of the exercise price over the amount realized upon the disposition of the shares of common stock.

The exercise of an Incentive Stock Option through the exchange of previously acquired stock will generally be treated in the same manner as such an exchange would be treated in connection with the exercise of an Non-Qualified Stock Option; that is, as a non-taxable, like-kind exchange as to the number of shares of common stock given up and the identical number of shares of common stock received under the Option. That number of shares of common stock will take the same basis and, for

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capital gain purposes, the same holding period as the shares of common stock that are given up. However, such holding period will not be credited for purposes of the one-year holding period required for the new shares of common stock to receive Incentive Stock Option treatment. Common shares received in excess of the number of shares of common stock given up will have a new holding period and will have a basis of zero or, if any cash was paid as part of the exercise price, the excess shares of common stock received will have a basis equal to the amount of the cash. If a disqualifying disposition (a disposition before the end of the applicable holding period) occurs with respect to any of the shares of common stock received from the exchange, it will be treated as a disqualifying disposition of the shares of common stock with the lowest basis.

If the exercise price of an Incentive Stock Option is paid with shares of common stock acquired through a prior exercise of an Incentive Stock Option, gain will be realized on the shares of common stock given up (and will be taxed as ordinary income) if those shares of common stock have not been held for the minimum Incentive Stock Option holding period (two years from the date of grant and one year from the date of transfer), but the exchange will not affect the tax treatment, as described in the immediately preceding paragraph, of the shares of common stock received.

SARs. Generally, a participant will not realize any taxable income upon the grant of a SAR and PCA will not be entitled to a deduction. Upon the exercise of the SAR, the participant will recognize ordinary income in an amount equal to the amount of cash and/or the fair market value, at the date of such exercise, of the shares of common stock received by the participant as a result of such exercise. PCA will generally be entitled to a deduction in the same amount as the ordinary income realized by the participant.

Full Value Awards. The federal income tax consequences of a Full Value Award will depend on the type of award. The tax treatment of the grant of shares of common stock depends on whether the shares are subject to a substantial risk of forfeiture (determined under Code rules) at the time of the grant. If the shares are subject to a substantial risk of forfeiture, the participant will not recognize taxable income at the time of the grant and when the restrictions on the shares lapse (that is, when the shares are no longer subject to a substantial risk of forfeiture), the participant will recognize ordinary taxable income in an amount equal to the fair market value of the shares at that time. If the shares are not subject to a substantial risk of forfeiture or if the participant elects to be taxed at the time of the grant of such shares under Code Section 83(b), the participant will recognize taxable income at the time of the grant of shares in an amount equal to the fair market value of such shares at that time, determined without regard to any of the restrictions. If the shares are forfeited before the restrictions lapse, the participant will be entitled to no deduction on account thereof. The participant’s tax basis in the shares is the amount recognized by him or her as income attributable to such shares. Gain or loss recognized by the participant on a subsequent disposition of any such shares is capital gain or loss if the shares are otherwise capital assets.

In the case of other Full Value Awards, such as restricted stock units or performance stock units, the participant generally will not have taxable income upon the grant of the award provided that there are restrictions on such awards that constitute a substantial risk of forfeiture under applicable Code rules. Participants will generally recognize ordinary income when the restrictions on awards lapse, on the date of grant if there are no such restrictions or, in certain cases, when the award is settled. At that time, the participant will recognize taxable income equal to the cash or the then fair market value of the shares issuable in payment of such award, and such amount will be the tax basis for any shares received. In the case of an award which does not constitute property at the time of grant (such as an award of units), participants will generally recognize ordinary income when the award is paid or settled.

PCA generally will be entitled to a tax deduction in the same amount, and at the same time, as the income is recognized by the participant.

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Plan Benefit Information

The specific individuals who will be granted awards under this new authorization and the type and amount of any such awards will be determined by the compensation committee, subject to the annual limits on the maximum amounts that may be awarded to any individual, as described above. Accordingly, future awards to be received by particular individuals are not presently determinable. During 2023, approximately 191,000 shares of restricted stock were awarded to all participants, of which 53,646 shares of restricted stock in total were issued to the named executive officers identified in the compensation tables presented in this proxy statement, and 5,724 fully vested shares were awarded as directors’ fees; and 122,926 performance units were awarded, of which 102,190 in total were awarded to the named executive officers identified in the compensation tables presented in this proxy statement.

Authorization of Securities under Equity Compensation Plans

Securities authorized for issuance under equity compensation plans at December 31, 2023 are as follows. The 1999 Long-Term Incentive Plan is the only plan under which equity incentive plan awards were made.

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PROPOSAL ON EXECUTIVE COMPENSATION

ITEM NO. 4 ON PROXY CARD

We are requesting our stockholders to approve an advisory resolution on the compensation for our named executive officers, which is more fully described in this proxy statement. Please refer to the “Compensation Discussion and Analysis” and “Executive Officer and Director Compensation” sections of this proxy statement immediately following to find information regarding the compensation paid to our named executive officers and a complete discussion of our compensation program.

We believe that our compensation is appropriate to further our business objectives, is competitive and aligns the interests of management and our stockholders. We believe that our program has been a key factor in the successful management of our company, driving our consistently strong performance in the paper and packaging industry. We discuss our compensation philosophy, the elements of compensation and our compensation decisions in more detail in the “Compensation Discussion and Analysis” immediately following.Analysis.”

We will continue to hold annual advisory votes on the compensation of our named executive officers until the next required stockholder advisory vote on the frequency of advisory votes on executive compensation. We are asking stockholders to approve the following advisory resolution at the 20182024 Annual Meeting:

RESOLVED, that the stockholders approve, on an advisory basis, the compensation of PCA’s named executive officers as disclosed in the Proxy Statement for the Company’s 20182024 Annual Meeting of Stockholders pursuant to the compensation disclosure rules of the Securities and Exchange Commission, including the Compensation Discussion and Analysis, the Summary Compensation Table and the related compensation tables.

This advisory resolution, commonly referred to as a“say-on-pay” “say-on-pay” resolution, isnon-binding on the board of directors and the company. Althoughnon-binding, we will carefully review and consider the voting results when evaluating our executive compensation program. Our current policy is to include an advisory resolution to approve the compensation of our named executive officers annually. Accordingly, unless we modify our policy on the frequency of future “say on pay” votes, the next advisory vote to approve our executive compensation will occur at the 2025 Annual Meeting of Stockholders.

The board of directors, based upon the recommendation of the compensation committee, unanimously

recommends a voteFORthe approval of the advisory resolution

approving our executive compensation

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COMPENSATION DISCUSSION AND ANALYSIS

Compensation Objectives

The compensation committee of our board of directors oversees the executive compensation program. The committee intends for the program to accomplish the following:

The committee believes that these objectives have been accomplished consistently, with the company’s management driving consistently strong performance in our industry and substantial returns for our investors since our inception.

20172023 Summary

PCA continued its strong performance in 2017,We entered 2023 with record earnings, productionchallenging business conditions, including significant cost inflation, lower demand for our products and corrugated products volume and continueddecreasing containerboard prices. We again demonstrated operational excellence during the year, focusing on providing outstanding service to our customers, execution of its growth strategy, culminating in substantial value creation for its shareholders. Earnings per share, excluding special items¹, improved from $4.88 in 2016internal capital investments to $6.02 in 2017. Reported earnings, including special items, improved from $4.75 per share in 2016profitably grow with our customers and careful management of our costs. Demand began to $7.07 in 2017. The company’s packaging segment, paper segmentimprove mid-year and whole company EBITDA margins led their respective industries, when compared to other domestic public companieswe experienced significant volume improvement in our industries. The company continuedcorrugated business that accelerated during the fourth quarter into 2024.

PCA’sOur stock price improved from $84.82 at the beginning ofperformed well during the year, continuing our track record of providing substantial returns to $120.55 at the end of the year. Through the end of 2017, PCA’sshareholders. Our one, three and five yearfive-year cumulative total shareholderstockholder return (assuming reinvestment of dividends) is as follows:

¹ Earnings per share excluding special items and free cash flow are Non-GAAP financial measures, which we present throughout this proxy statement. Important information relating to our use of these Non-GAAP financial measures and a reconciliation of these Non-GAAP financial measure to the most comparable financial measure presented in accordance with Generally Accepted Accounting Principles (GAAP) are included on Appendix A to this proxy statement.

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2023 Compensation Program Summary

PCA regularly reviews its compensation program and structure, both to assure appropriate incentives to drive industry-leading performance and alignment with the expectations of its shareholders. During 2023, FW Cook served as our independent consultant and, among other things, assisted with the ongoing review and assessment of our compensation practices. PCA annually reviews its compensation against a peer group in terms of amount and structure.

PCA’s compensation program emphasizes long-term performance, with equity awards comprising the majority of compensation for all of our named executive officers and with two-thirds of those awards subject to the achievement of rigorous long-term performance goals. PCA’s annual incentive compensation levelsis also paid out subject to objective performance measures.

PCA does not contractually entitle any executive officer to severance payments and does not have employment agreements with its officers. We have robust stock ownership guidelines (six times base salary for 2017our CEO), substantial stock ownership among our executive officers and policies to prevent our officers from hedging or pledging stock. Our equity incentive plan prohibits repricing of awards and does not utilize “single trigger” vesting upon a change of control.

Our CEO’s 2023 target awarded compensation was $13.5 million and actual awarded compensation was $14.3 million. “Awarded compensation” includes salary, the grant date fair value of stock awards and the annual cash incentive award. The elements of compensation were as follows:

PCA’s actual awarded compensation for 2023 for our CEO increased approximately 18% from 2022 awarded compensation. The increase was primarily due to a higher annual incentive compensation and long-term equity compensation. PCA’s annual cash incentive awards increased by approximately 6% primarily as a resultvalue of record earnings and strong margin performance. PCA increasedthe annual equity compensation by approximately 10%, primarily reflecting a higher year-over-year stock price ataward, which is discussed in more detail later under the time of the awards ($107.71 in 2017 compared to $67.57 in 2016). Our total compensation in 2017 also includedcaption “Long Term Equity Awards.”

Comparative Assessments

Consistent with our compensation objectives described above, our executive compensation program is designed to be competitive with the programs that are offered at paper, packaging and related manufacturing companies comparable to us. While comparing our compensation to other companies may not always be totally appropriate due to aspects of our business, these comparisons assist the committee’s decision makingdecision-making process.

At the directionWe annually obtain an assessment of the committee, we have retained Meridian Compensation Partners, LLC, a nationally recognized compensation consulting firm, to assess the compensation of our named executive officers relative to a group of named executive officers at other peer companies and providethat provides us with information in support of our compensation practices. The assessments include the compilation of compensation data from the peer group companies selected by management and approved by the committee, and the comparison of the compensation of each of our named executive officers relative to similar officers at the peer group companies. Representatives of Meridian and other consultants have not attended meetings of the compensation committee and have not otherwise participated in any compensation decisions or the design of our executive compensation program.

Compensation is compared to a peer group designed to include: (1) direct industry competitors, (2) companies viewed by PCA and its investors as operating in related paper, packaging or container industries or in the basic materials sector and that are comparable in size or scope, across such measures as total revenues, taking into account the integrated nature of PCA’s business, and market capitalization; (3) other companies of similar size and scope in the basic materials

PCA’s 20172023 revenues are slightly abovebetween the 25th percentile and the median of the group, its market capitalization is betweenabove the median and 75^th75th percentile of the group, its one-year total stockholder return is above the 75th percentile of the group and itsone-year total stockholder return and its three-year total stockholder return were aboveis between the 75^thmedian and the 75th percentile of the group.

In May 2017, Meridian completedAnnually, our compensation consultant completes a compensation assessment against the peer group, using the most recently filed proxy statements and public filings to obtain comparative 2016 compensation data.

The committee uses these assessmentsthe assessment to help ensure that our executive compensation is competitive and appropriately reflective of performance.in line with industry and market practice. The committee also uses these assessments as a guide when determining each element of incentive compensation, the mix of base salary, annual performance-based, cash incentive awards and equity grants within the overall compensation package, and the total compensation compared to the peer group companies. There is nopre-established policy or target for the mix between cash andnon-cash, or short and long-term incentive compensation though the substantial majority of compensation awarded to our top two officers is in the form of long-term equity compensation.

Mr. Mundy’s 2016 compensation was at the median of the CFOs of the peer group, with cash compensation the highest in the peer group and equity compensation the lowest in the peer group.

Actual Performance. In January 2024, after 2023 results were finalized, the committee made award determinations in accordance with the payout matrix, based upon actual earnings per share, excluding special items, exceeded the initial annual operating planof $8.70.² The matrix yielded a payout at 134% of target of $5.65 per share, and was lower than the pricing-adjusted target of $6.27 per share. The primary reason that earnings were lower than the adjusted target was that input costs, particularly relating to recycled fiber, were higher than assumed in the plan. In light of business conditions, with strong demand and cost inflation, the committee was satisfied with our earnings performance, noting that we maintained high margins and achieved volume growth.

instead of a more commonly used 200% and performance at or above the ROIC performance units will be paid out in shares of our common stock. 90th percentile is required to pay above target.

The amount paid out isunder the ROIC Units and the TSR Units will be determined based upon our average returnperformance on invested capitalthe applicable performance measure compared to a peer group consisting of the following companies: AptarGroup, Inc; Bemis Company;Avery Dennison Corporation; Berry Plastics Group,Global, Inc.; Cascades, Inc.; Celanese Corporation; Clearwater Paper Corporation; Crown Holdings, Inc.; Domtar Corporation; PH Glatfelter Co.; Graphic Packaging Holding Company; Greif, Inc.; International Paper Company; KapStone Paper and Packaging Corporation; Owens-Illinois, Inc.; Resolute Forest Products,OI Glass, Inc.; Sealed Air Corporation; The Sherwin Williams Corporation; Silgan Holdings Inc.; Sonoco Products Co.; Sylvamo Company; and WestRock Company. Holders will also receive dividend equivalents upon vesting with a value equal to the amount of dividends accrued on the shares that actually vest. Dividend equivalents will be paid in cash unless the committee determines to pay them in shares.

The peer group wasis intended to be a comprehensive group of publicly traded paper, packaging and packagingother industrial companies, which may compete with us for investor capital. The peer group was not changed from 2022, except to remove Resolute Forest Products, which was acquired during the same as theyear. This group used for units awarded in 2015 and 2016 and is not intended to be the same group used for comparative assessments as described above under “ — “—Comparative Assessments.”

AnnualFor the ROIC Units, annual return on invested capital for PCA and each peer company will be calculated for 2018, 2019each of 2023, 2024, 2025 and 20202026 and averaged. Return on invested capital meanspre-tax operating profit before publicly reported special items divided by the sum of totalnet debt and total equity.

The unitsROIC Units will vest on, June 21, 2021,and pay out on or promptly after, February 22, 2027, the fourth anniversary of the date of the award, as long as the recipient is employed by, or otherwise provides services to, PCA. PCA must perform above the median of the group for the ROIC units to pay out at or above target. If PCA performs in the top quartile ofthree companies in the group, a number of shares equal to 100% of the units will be paidpay out with the committee having discretion to award up to an additional 20%.at 120% for first place, 113.33% for second place and 106.66% for third place. If PCA performs in the second quartile of the group, 80% ofbetween median and fourth place, the units will be paidpay out with the committee having discretion to award up to an additional 20%at 100%. If PCA performs in the third quartile of the group, a number of shares between 40% and 100% of the unitstarget number of shares will be paid out, with the committee having the discretion to award an additional 40%.pay out. If PCA performs in the fourth quartile, thereno shares will vest.

For the TSR Units, total stockholder return for PCA and each peer company will be calculated for the period beginning on March 1, 2023 and ending on February 28, 2026 with the beginning and ending Stock price determined on a 20-day, volume weighted average price basis preceding such dates. The TSR Units will vest and pay out after certification of performance by the committee promptly after the end of the performance period. PCA must perform above the median of the group for the TSR Units to pay out at or above target. If PCA is the highest performer in the peer group, 200% of the target number of shares will vest. If PCA performs between the median and the highest performer of the group, a number of shares between 100% and 200% of the target number of shares will vest. If PCA performs between the 33.33rd percentile and the median, a number of shares between 0% and 100% of the target number of shares will vest. If PCA performs below the 33.33rd percentile, then no payout.shares will vest. The actual number of shares vesting within each range will be determined based upon linear interpolation of PCA’s performance within that range.

The terms of the units are consistent with prior years.

2023 Award Levels. Our historical approach has been to vary award levels based upon the change in our stock price; i.e., higher or lower stock price drives higher or lower absolute award levels for each officer, and we consider individual adjustments based upon competitive market information, individual performance, retention needs or changes in responsibilities. As further described below, award levels were increased by approximately 33% for each of Mr. Kowlzan and Mr. Hassfurther. Award levels were down approximately 2% for each of the other officers to reflect a slightly lower year-over-year stock price.

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Mr. Kowlzan and Mr. Hassfurther each have nearly 15 years in their current positions as CEO and leader of our corrugated business, respectively making them longer tenured than rest of the peer company officers to whom they are compared. Since July 1, 2010, when Mr. Kowlzan was promoted to CEO and approximately one year after Mr. Hassfurther was promoted to his position, the company’s aggregate total shareholder return is in excess of 1000%, more than doubling the return of the S&P 500 during that time. They are the stewards of our strategy, focusing on profitable growth from unyielding service to our customers, operational excellence and disciplined and balanced capital allocation in furtherance of these goals. While both are at or around retirement age, each has indicated to our board as part of the board’s ongoing succession process, that he is willing to serve for multiple years while continuing to develop internal candidates who can take over their positions and continue our company’s success.

In light of the importance of retaining Mr. Kowlzan and Mr. Hassfurther as they continue to execute upon our strategy and develop internal succession candidates, the board believes that it is in the best interest of shareholders to provide an appropriate incentive for such retention. In consultation with our compensation consultant, the compensation committee determined to provide a 33% increase in the long-term incentive portion of their compensation, which is heavily weighted towards performance-based compensation that is subject to the attainment of rigorous long-term performance goals and has no provision for vesting on retirement. The committee may consider factors it determines to bebelieves these award levels are appropriate in connection withlight of historical performance and the discretionary vesting, including ranking withinimportance of continuing the quartile and business conditions that drove performance during the period.company’s success.

Annual awards are made to the named executive officers on the same date as other plan participants. Historically, the grant date has been between June 12th and July 2ndPayout of each year. We have chosen to pay cash incentive awards at the beginning of the year, and to make equity grants nearmid-year. This timing gives us an opportunity to discuss with the named executive officers and other key managers their compensation and

service earned under both the new PCA Pension Plan and the prior Pactiv pension plan. Benefits earned under the PCA Pension Plan are reduced by retirement benefits earned under the Pactiv pension plan through April 30, 2004. All assets and liabilities associated with benefits earned through April 30, 2004 for our salaried employees and retirees were retained by the Pactiv pension plan.

In addition to the PCA Pension Plan, Mr. Kowlzan, Mr. Hassfurther and Mr. HassfurtherShirley participate in a PCA supplemental executive retirement plan (the “SERP”). Benefits are determined using the same formula as the PCA Pension Plan but in addition to counting career average base pay, the SERP also recognizes incentive awards and any pay earned in excess of IRS qualified plan compensation limits. Benefits earned under the SERP are reduced by benefits paid from the PCA Pension Plan and any prior qualified pension and SERP benefits earned under the Pactiv pension plan.

Mr. Mundy Mr. Carter and Mr. PfledererCarter do not receive any pension benefits because they joined PCA after April 12, 1999.12,1999.

401(k) Plan

We offer a defined contribution 401(k) plan to our salaried employees, including the named executive officers. We have historically provided to PCA employees a company matching contribution of up to 5.2% of

than what are generally available to our salaried employees who are eligible to participate in our various compensation plans. However, the committee will consider post-retirement or post-termination arrangements and acceleration or continued vesting of certain equity awards for named executive officers on acase-by-case basis. basis in the event of a retirement or termination.

Payments Made Upon Termination

In general, when a named executive officer terminates employment with us, other than a termination for cause, the named executive officer is entitled to receive the amounts they have earned during the term of their employment and any benefits allowed as part of our compensation plans. These amounts that they will receive include the following:

Payments Made Upon Death or Disability

In the event of the death or disability of a named executive officer, in addition to the items identified above, all named executive officers will receive benefits under our disability plan or payments under our life insurance plan, as appropriate. Under our equity incentive plan, upon death or disability, generally all restrictions on restricted stock will lapselapse. In the event of death (a) the TSR Units will vest on the date of death and pay out a pro-rated portion through the date of death of the holder, based upon actual performance unitsthrough the date of death; and (b) ROIC Units will be paidvest on the date of death and pay out based upon actual performance through the calendar year preceding the date of death (or at 100%the target level if the date of death is before the end of the first year of the performance period).

Tax Implications

The committee has considered the provisions of Code Section 162(m), which generally limits the annual tax deductibility of compensation paid to each named executive officer to $1 million. To the extent possible,Therefore, we expect that compensation paid to our covered executive officers in excess of $1 million is not deductible. Although the committee intendswill continue to preserve the federal incomeconsider tax deductibility but may choose to provideof compensation that may not be deductible if itas one of many factors, the committee believes that such payments are appropriateit is in the best interests of our shareholders and our company to ensure that our named executive officers receive total compensation that is competitive with our peer group, reflects superior performance or otherwise achievesmaintain the flexibility to structure our compensation objectives, such as the motivationprograms to appropriately and retention of our executive officers. The Code Section 162(m) performance factors and annual grant limitations under the Performance Incentive Plan and Long-Term Equity Incentive Plan are intended to enable us to provide incentive compensation to certain ofcompetitively compensate our executive officers, even if these programs may result in a manner that qualifies for an exemption, as “performance-based compensation”, from the deduction limitations under Section 162(m). As recent tax legislation has eliminated the ability to deduct “performance based compensation” in 2018 and beyond, our ability to deduct “performance based compensation” will be limited to certainnon-deductible compensation awarded prior to the end of 2017 to the extent permitted by the transition rules included in such legislation.expense.

Policies Applicable to Executive Officers

Trading in Our Stock

Our trading policy prohibits our directors and executive officers from participating in short-swing trading, short selling or entering into anypledging our stock. Our policy prohibits hedging transactions, including transactions in options and other derivative securities relatedrelating to their ownership of ourPCA common stock or pledging our stock.in any market. All transactions in PCA common stock by our directors and executive officers are subject to trading

relevant. Shares that count towards satisfaction of the guidelines include: (1) shares owned outright by the participant or an immediate family member that shares the same household; (2) shares held in our defined contribution plans; and (3) restricted stock or restricted stock units issued by us, whether or not vested. Shares underlying option awards and performance units (prior to certification of achievement of the performance goals) do not count toward achievement of the share ownership guidelines.

Participants are required to achieve their guideline within five years of becoming subject to the guidelines. The committee has the authority to review each participant’s compliance (or progress towards compliance) with the guidelines from time to time. In its discretion, the committee may impose conditions, restrictions or limitations on anynon-compliant participant as the committee determines to be necessary or appropriate.

All of ournon-management directors and named executive officers are in compliance with or are achieving adequate progress towards, the guidelines.

EXECUTIVE OFFICER AND DIRECTOR COMPENSATION

Summary Compensation Table

The grant date fair value of restricted stock awarded is the closing price of PCA common stock on the date of the award.

The grant date fair values of the ROIC Units awarded in 2023 (as described in “Compensation Discussion and Analysis—Long-Term Equity Awards—Equity Award Structure”), based upon the probable outcome of the performance conditions, which was 100%, are $3,201,621, $2,216,683, $726,814, $616,613, and $465,458 for Mr. Kowlzan, Mr. Hassfurther, Mr. Mundy, Mr. Carter and Mr. Shirley, respectively. The grant date fair values of the awards at a maximum payout of 120% are $3,851,945, $2,660,019, $872,177, $739,936, and $558,549 for Mr. Kowlzan, Mr. Hassfurther, Mr. Mundy, Mr. Carter and Mr. Shirley, respectively.

The grant date fair values of the TSR Units awarded in 2023 (as described in “Compensation Discussion and Analysis—Long-Term Equity Awards—Equity Award Structure”) as determined based upon a Monte Carlo simulation as prescribed by FASB ASC Topic 718 are $3,201,664, $2,216,674, $726,832, $616,512, and $465,548 for Mr. Kowlzan, Mr. Hassfurther, Mr. Mundy, Mr. Carter and Mr. Shirley, respectively. The grant date fair values of the awards at a maximum payout of 200% are $6,403,329, $4,433,349, $1,453,664, $1,233,024 and $931,096 for Mr. Kowlzan, Mr. Hassfurther, Mr. Mundy, Mr. Carter and Mr. Shirley respectively.

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