How to Merge PDFs With Different Page Sizes
By PDFOak · Published September 9, 2026 · Updated October 1, 2026
Merge the files, then look at the points where the page size changes, in the viewer your reader will use.
Mixed sizes are valid PDF, and they are common in reports that include wide tables.
Why mixed sizes work
A PDF page owns its own media and crop boxes, so the next page can be wider, taller or landscape without making the document invalid. Viewers fit each page to the window, so the difference can look subtle on screen and become obvious on paper.
Plan for printing
A printer may scale each page to the paper tray you selected. If the physical output has to be uniform, prepare standard-sized source pages on purpose instead of relying on an unknown printer setting.
Rotation and page size are separate. A landscape page is not necessarily sideways.
What to check
- Note the size and orientation of each source.
- Arrange the files in reading order.
- Merge without printing or resizing.
- Review every place the page size changes.
- Rotate only the pages that are actually sideways.
Frequently asked questions
Why do pages print at different scales?
The printer fits each page’s dimensions onto the paper size you chose, so a Letter page and an A4 page can land at slightly different scales.