Decide the order of the final document first
If you need to submit a quote, a manual and supporting PDFs as one file, write down the order in which they should be read, from the first file in the list to the last. This tool does not read the content to work out the document order. It joins every page of each PDF in exactly the order the files appear in the on-screen list.
Adding 01, 02 to the start of file names helps when you organize the originals, but do not assume the file picker always hands files over in that order. After selecting, check the list numbers and the first-page thumbnails again.
Adding files and changing their order
Open the ‘Merge PDF’ tab in the PDF tools and select your files. It accepts up to 10 files at a time, up to 50MB each. Drag files in the list or use the up and down arrows to change their position, then press the merge-and-download button.
Adding files again through the file picker does not append them to the existing list; it replaces the list with the files you just selected. If a file is missing, select all the files you need together again. If a thumbnail does not appear, check the original in a separate PDF viewer.
Example: using page counts to find missing pages
As an illustrative example, if A has 2 pages and B has 3 pages, merging A→B gives a 5-page result. Pages 1–2 should be A and pages 3–5 should be B. If you moved B to the top, pages 1–3 should be B and pages 4–5 should be A.
Do not stop at confirming that there are two files. Compare the sum of each file’s page count with the page count of the final PDF. Even if the totals match, you may have added the same document twice, so also read the pages on either side of each document boundary.
When merging stops or the result looks different
Password-protected or damaged documents may not be processed like ordinary PDFs. There is no feature for bypassing passwords. Export the original again from a copy you have permission to open and edit, then try again.
The tool creates a new PDF by copying pages, so it does not guarantee that electronic signatures or document-level bookmarks, attachments and form behavior are preserved. For signed documents and official submissions, keep the originals and open the result to check it yourself.
Technical source: pdf-lib, used to copy pages · Checked 2026-10-11
Check three points before you save
Check the first page of the result, each page where two different files meet, and the last page. Make sure you did not overwrite an original with the result, that the total page count matches, and that pages mixing landscape and portrait still read in a sensible orientation. If you find a file that should not be there, fix the list and create a new result.
Keep the original and check the content, size and format of the result.