Reg FD Disclosure

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549     FORM 8-K     CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): December 10, 2025     Packaging Corporation of America (Exact name of registrant as specified in its charter)       Delaware   1-15399   36-4277050 (State or other jurisdiction of incorporation)   (Commission File Number)   (IRS Employer Identification No.) 1955 West Field Court , Lake Forest , Illinois 60045 (Address of Principal Executive Offices, including Zip Code) (847) 482-3000 (Registrant’s Telephone Number, Including Area Code)     Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrants under any of the following provisions:   ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)   ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)   ☐ Pre-commencement communications pursuant to Rule 14d-2 (b) under the Exchange Act (17 CFR 240.14d-2 (b))   ☐ Pre-commencement communications pursuant to Rule 13e-4 (c) under the Exchange Act (17 CFR 240.13e-4 (c)) Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter). Emerging growth company  ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ Securities registered pursuant to Section 12(b) of the Exchange Act:   Title of each class   Trading Symbol(s)   Name of each exchange on which registered Common Stock   PKG   New York Stock Exchange       Item 7.01. Regulation FD Disclosure The following information, including the exhibit described below, shall not be deemed “filed” hereunder for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing. On December 10 and 11, 2025, Mark W. Kowlzan, PCA’s Chairman and Chief Executive Officer and Kent A. Pflederer, PCA’s Executive Vice President and Chief Financial Officer will conduct meetings with analysts and investors. The slides to be used are furnished herewith as Exhibit 99.1 and incorporated by reference into this Item 7.01.   Item 9.01. Financial Statements and Exhibits. (d) Exhibits   99.1    Slide presentation to be dated December 10-11, 2025 104    Cover Page Interactive Data File (embedded within the Inline XBRL document) SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.   PACKAGING CORPORATION OF AMERICA By:   /s/ Kent A. Pflederer   Executive Vice President and Chief Financial Officer Date: December 10, 2025