Interleave PDF
Zip-merge pages from two documents alternately.
How to use Interleave PDF
- 01
Add both PDFs
Drop in the two documents you want to combine — typically the front sides and the back sides of a duplex scan.
- 02
Pages are zipped together
The tool alternates pages: the first from document A, the first from document B, the second from A, the second from B, and so on.
- 03
Download the reassembled PDF
Save one document with the pages interleaved in the correct reading order.
Tested and last verified on
About Interleave PDF
Combine two PDFs by alternating pages — A1, B1, A2, B2… Perfect for merging odd/even scanned pages from duplex scanners, or combining front and back scans into one document.
Rebuilding a double-sided scan from two passes
If your scanner can only capture one side of a page at a time, the usual way to digitise a double-sided stack is in two passes: scan all the fronts into one file, flip the stack, and scan all the backs into another. That leaves you with two separate PDFs that are useless on their own — you need them woven back together so page one's front is followed by page one's back, then page two's front, and so on. Interleaving does exactly that, alternating pages from the two documents to reconstruct the original as it was printed.
You simply add the two files and download a single combined PDF with the pages zipped together in the right sequence. It turns a fiddly, error-prone manual reordering job — where one misplaced page throws off everything after it — into a single reliable step.
Getting the order right, and related tools
The one thing to watch is the order of your back-sides file. Because you flip the stack before the second pass, the backs are often captured from the last sheet to the first — so before interleaving, run that file through Reverse PDF to put it in the same direction as the fronts. Once both files run in the same order, interleaving lines them up perfectly. This workflow is the natural partner to the Extract Odd Pages and Extract Even Pages tools, which do the opposite job of pulling a mixed scan apart into its fronts and backs.
Everything is processed in your browser, so reassembling a scanned contract, ledger or medical file keeps every page on your own device. There's no account, no queue and no watermark, and your source files are left unchanged, so you can adjust the order and interleave again if the first attempt doesn't line up the way you expected. That makes it painless to get right on the first real try: test with a couple of pages, confirm the fronts and backs align, then run the full stack with confidence.
Questions
Everything runs in your browser. How we keep files private
What is interleaving actually for?
Its main job is rebuilding a double-sided document that was scanned in two one-sided passes: one file of all the fronts and another of all the backs. Interleaving zips them back together into the original front-back-front-back order.
My back-sides file is in reverse order — what do I do?
That's common, because scanning a flipped stack captures the backs from last to first. Run that file through the Reverse PDF tool first, then interleave, and the fronts and backs will line up correctly.
What if the two documents have different page counts?
Interleaving alternates pages for as long as both documents have them and then appends whatever is left over, so a small mismatch won't stop it from producing a combined file.
Is this done privately in my browser?
Yes. Both files are combined locally on your device, with nothing uploaded to a server.