Interleave PDF Pages
Interleave two or more PDFs into one — put separate odd-page and even-page scans back in the right order (A1, B1, A2, B2…), or re-order one two-sided scan.
Drop the odd / front-side PDF here (pages 1, 3, 5 …)
Drop the even / back-side PDF here (pages 2, 4, 6 …)
🔒 Processed in your browser — never uploaded.
Combine a two-part scan back into one document
If your scanner only reads one side at a time, the usual trick is to scan every front page into one PDF, flip the whole stack, and scan every back page into a second PDF. This tool weaves those two files back together in the real reading order — page 1 from the first file, page 1 from the second, page 2 from the first, and so on (A1, B1, A2, B2 …). If one file has more pages than the other, the leftover pages are added at the end. When the back sides come out last-page-first — common when a duplex feeder flips the stack — turn on that file’s reverse option before merging. It is not limited to two files: once both dropzones are filled a third appears that takes as many more as you like, and every file gets its own row — its page count, which direction to read it in, how many of its pages to take per turn (put 3 on one file and one page of another is slotted between every three of it), and buttons to move it earlier or later. If your scanner produced a single file holding every front followed by every back, drop it in on its own and tick the one-file option: it is split down the middle and put back into reading order — 1, n, 2, n-1 … — with no need to split it first.
Private, in your browser
Everything runs locally with pdf-lib: your PDFs are read, interleaved, and saved on your device and never uploaded to any server, so it works offline and keeps confidential scans private. Pages are copied exactly as they are, without re-rendering or quality loss. Each file’s page count is shown as soon as it lands and you are told when they differ, and the first six pages of the woven result are drawn for you before you download anything, so the order is something you look at rather than guess.
Frequently asked questions
When would I need to interleave two PDFs?
Most often after scanning a double-sided document on a single-sided (simplex) scanner: you scan all the odd/front pages into one file, flip the stack, and scan all the even/back pages into another. This tool merges them back into the original 1, 2, 3, 4 … order in one step.
What does the reverse back pages option do?
Every file in the list has its own “Read backwards” box, which takes that file’s pages from its last page first. When you flip a stack of pages to scan the backs, they often feed in from the last page to the first, so the even-page PDF ends up in reverse; ticking its box puts those pages back in the right order.
Can I interleave more than two PDFs?
Yes. The first two dropzones name the fronts and the backs; once both are filled a third appears that accepts any number of extra files. Each one gets a row showing its page count, with its own direction, its own number of pages to take per turn, and buttons to move it earlier or later or take it out. The weave goes through the files in the order the list shows, and a file that runs out of pages simply drops out of the rotation.
My scanner made one file with all the fronts and then all the backs. Can I fix that here?
Yes — drop it in on its own and tick “This one file holds all the fronts and then all the backs”. The file is split down the middle and woven back into reading order: 1, n, 2, n-1 … A second box says whether the backs were scanned in reverse, which is what happens when the stack is flipped; turn it off if the backs were fed in the same order as the fronts. You do not have to split the file into two first.
Are my PDFs uploaded anywhere?
No. Every file you add is read and merged entirely in your browser with pdf-lib. Nothing is sent to a server, so even confidential scans stay on your device and the tool works offline.