SCHEDULE 13G/A 0000902664-24-001620 0001771944 XXXXXXXX LIVE 3 Common Stock, par value $1.00 per share 09/30/2025 0001333274 MERCER INTERNATIONAL INC. 588056101 700 WEST PENDER STREET SUITE 1120 VANCOUVER, British Columbia A1 V6C 1G8 Rule 13d-1(b) Boundary Creek Advisors LP DE 0.00 00.00 0.00 0.00 0.00 N 0 IA PN Peter Greatrex X1 0.00 0.00 0.00 0.00 0.00 N 0 HC IN MERCER INTERNATIONAL INC. Suite 1120, 700 West Pender Street, Vancouver, British Columbia, Canada V6C 1G8 This statement is filed by: (i) Boundary Creek Advisors LP (the "Investment Manager"), a Delaware limited partnership, and the investment adviser to Boundary Creek Master Fund LP (the "Boundary Creek Fund"), with respect to the shares of common stock, par value $1.00 per share (the "Common Stock") of Mercer International Inc. (the "Company") that were directly held by the Boundary Creek Fund; and (ii) Mr. Peter Greatrex ("Mr. Greatrex"), the managing member of Boundary Creek Partners LLC, the general partner of the Investment Manager, with respect to the shares of Common Stock that were directly held by the Boundary Creek Fund. The foregoing persons are hereinafter sometimes collectively referred to as the "Reporting Persons." The address of the business office of each of the Reporting Persons is 340 Madison Avenue, 12th Floor, New York, NY 10173. The Investment Manager is a Delaware limited partnership. Mr. Greatrex is a citizen of the United States. N IA HC The information required by Item 4(a) is set forth in Row 9 of the cover page for each of the Reporting Persons and is incorporated herein by reference. 0% The information required by Item 4(c)(i) is set forth in Row 5 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The information required by Item 4(c)(ii) is set forth in Row 6 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The information required by Item 4(c)(iii) is set forth in Row 7 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The information required by Item 4(c)(iv) is set forth in Row 8 of the cover page for each of the Reporting Persons and is incorporated herein by reference. N Y Y Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11. Boundary Creek Advisors LP /s/ Peter Greatrex 11/07/2025 Peter Greatrex /s/ Peter Greatrex 11/07/2025