Merge PDF files
Combine multiple PDF files into one, in the order you choose, or interleave alternating pages from two or more files (for recombining separately-scanned front and back sides).
How it works
- Add two or more PDF files.
- Choose Merge in order (use the arrows to set file order) or Interleave (alternate pages) for duplex scans, with an option to reverse the second file if its pages came out of the scanner back to front.
- Choose Merge or Interleave and download the combined PDF.
How the order works
The merged PDF follows the list from top to bottom. Suppose you add three files in this order:
| Position | File | Pages | Pages in the merged PDF |
|---|---|---|---|
| 1 | cover-letter.pdf | 1 | 1 |
| 2 | passport-scan.pdf | 2 | 2 to 3 |
| 3 | bank-statement.pdf | 4 | 4 to 7 |
The result has 7 pages. Move bank-statement.pdf to the top with the arrows and it becomes pages 1 to 4, followed by the cover letter on page 5 and the passport scan on pages 6 and 7. Page order inside each file does not change.
To reorder pages after merging, use Reorder PDF pages. To keep only some pages of a file before merging, use Delete or extract pages. To cut the merged file apart again, use Split PDF.
What happens to the file size
Merging joins the pages; it does not recompress them. The merged file is typically close to the total of the inputs, and can differ a little either way. If a portal limits the file size, merge first, check the size shown in your file manager, then see how to get a PDF under a size limit. To shrink a PDF that already exists, use Compress PDF; merging does not recompress anything. See upload limits by portal for the limits we have read.
Interleaving two scans (front and back sides)
Switch to Interleave (alternate pages) instead of Merge in order when you have scanned the front sides of a double-sided document as one file and the back sides as another. The tool takes one page from each file in turn — page 1 of the first file, page 1 of the second, page 2 of the first, and so on — so the result reads front, back, front, back in the right order.
Most flatbed and sheet-fed scanners produce the back sides in reverse order, because you flip the whole stack over and scan it again without reordering the pages first. Tick "Reverse the second file's page order" to correct for that before interleaving.
If one file has fewer pages than the other (a missing back side, for example), that file is simply skipped once its pages run out, and the remaining file's pages are appended in order — nothing is padded with a blank page and nothing is silently dropped.
Password-protected PDFs and current limitations
A password-protected PDF is not merged. The tool shows the message "This PDF is password-protected. Remove the password before processing it here." and asks you to remove the password first. There is no unlock tool on this site yet.
- Each file can be up to 100 MB and 2,000 pages (250 MB with a signed-in Pro subscription).
- Pages are merged or interleaved whole. You cannot pick pages inside this step; extract them first.
- We have not tested whether bookmarks, form fields or tagged-PDF accessibility structure survive a merge. If you rely on them, check the merged file.
- Page numbers are not added automatically. Use Add page numbers afterwards.
Good to know
- Free files are capped at 100 MB; a signed-in Pro subscription raises that to 250 MB. The higher limit hasn't been measured beyond the original 100 MB fixture size — very large merges may still be slow on a phone.
Frequently asked questions
- Are my PDFs uploaded when I merge them?
- No. The merge runs in your browser and the files stay on your device.
- Can I choose the order of the files?
- Yes. The merged PDF follows the order of the list, and you can move files up or down with the arrows before merging.
- Will merging make the file bigger?
- The result is roughly the sum of the inputs. If an application has a size limit, merge first and check the size, then reduce the source scans if needed.
- How do I recombine a double-sided scan I did as two separate files?
- Choose Interleave (alternate pages) instead of Merge in order. If the back-side file came out of the scanner in reverse order (common when you flip the whole stack over), tick the option to reverse it first.