Merging PDFs With Different Page Sizes: Why the PDF Organiser Counts A5 and Legal as Other

I work on OnePassApps, the team behind app.onepassapps.com. This is our own PDF Organiser.

When you merge PDF files whose pages are different sizes, something has to give: one sheet size for all of them, or one size per page. Our PDF Organiser does the second one. Each page keeps the size it arrived with, and the exported file proves it.

The Paper row names two sizes and stops there

I loaded five one-page PDFs into the PDF Organiser in one browser session: A4 (595.92 x 841.92 pts), US Letter (612 x 792 pts), US Legal (612 x 1008 pts), A5 (420 x 595.92 pts) and a custom 7 x 9 inch sheet (504 x 648 pts). The Source step read "5 of 20 PDFs" and "5 of 300 pages".

The Export step has a Paper row. With those five sheets loaded it reads:

Paper
1 A4 - 1 Letter - 3 other

Two sizes are named, and the count is right: there is one A4 page and one Letter page. Everything else is folded into "other". The Legal, the A5 and the custom sheet are three pages, and the panel calls them "3 other". So the row is a summary of how many pages sit on each size, not a list of every size in the file. If you are checking a merge by paper size, that is the line to read - and if you expected it to name your Legal or A5 sheet, or to print their dimensions, it will not.

An earlier post of mine measured this same row on 7 November 2026, when it read in millimetres for each distinct size instead. I have linked it at the end rather than repeat it: this is the same app and the same question, answered from today's build.

Nothing is resized

I pressed "Download PDF" and read the exported file back page by page with pdfinfo:

Page 1: 595.92 x 841.92 pts (A4)
Page 2: 612 x 792 pts (letter)
Page 3: 612 x 1008 pts
Page 4: 420 x 595.92 pts (A5)
Page 5: 504 x 648 pts

Every page came out at the size it went in at. The A4 page was not stretched to Letter, the A5 page was not scaled up, and the custom sheet was not snapped to anything. On a four-page run (A4, Letter, A5 and the custom sheet) pdftotext pulled the four headings back out of the export in order, so the content came through with the sizes.

Rotation travels with the page

With four sheets loaded I pressed "Rotate right" on the first page tile. The panel moved to "Rotated 1 of 4 pages", and the exported file carried it as page 1 rot 270 - the other three pages stayed at rot 0. The turn is written as a page rotation flag, not by swapping the width and height of the page box, so the page box itself is unchanged.

What the export offers, and what I could not reach

The Export step lists two things: "Combined PDF", with the line "organised.pdf - up to 64 MiB", and "Split ZIP", with the line "up to 50 pages - 50 MiB".

I could not run the Split ZIP export. The export area holds no radio inputs at all, and the only export button on the page is "Download PDF". Clicking the "Split ZIP" label itself changed nothing - the export buttons and the Paper row were identical afterwards. So the ZIP is described in the panel, and I am not claiming I produced one. The guide repeats it as part of the app's scope: "Merge, split, reorder, and rotate existing PDF pages locally."

The panel also carries one warning worth reading before you rely on a merge: "Page content is preserved. Bookmarks, forms and digital signatures may not carry over to a new export."

The limits it states

The Source step reads "Up to 20 PDFs, 25 MiB each, 50 MiB combined and 300 pages. Encrypted PDFs are not supported." The app's own guide puts the same numbers in a different order: "Imports allow up to 20 files, 25 MiB per file, 50 MiB combined and 300 pages."

The page says "Nothing leaves this tab." I traced the network while the export ran: 137 requests, and every one of them was a GET. No PDF byte was posted anywhere.