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Interleave two PDF scans

Scanned the fronts, flipped the stack, scanned the backs? Drop both files and get one document in the right order.

Files are processed entirely in your browser. Your file's contents never leave your device.

Your PDF never touches a server. There's nothing here to ration.

No daily caps. No spinner that turns into a paywall after the third file.

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Your PDF never leaves your device.

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Doing the same few steps to a folder of PDFs? Run several tools in one pass

About this tool

Scanning a double-sided document on a scanner that only reads one side leaves you with two useless halves. The first pass through gives you the fronts (pages 1, 3, 5, 7), and then you flip the whole stack over and run it again, which gives you the backs in reverse: 8, 6, 4, 2, because the last sheet is now on top. Neither file is the document. Ordinary merge does not help either, because it concatenates: you get every front followed by every back, still out of order, and nothing warns you that the result is wrong.

Interleaving takes one page from each file in turn instead, so the two halves zip back together into 1, 2, 3, 4. Because the flipped stack is the normal case, the second document is set to reverse automatically. And because that is the one setting people get wrong, it is a visible checkbox on each file, with a preview of the exact page order underneath. Files of unequal length are fine: an odd number of sheets leaves the backs one page short, and the leftover page is kept at the end rather than dropped.

The whole reassembly happens in your browser. Scans are the most personal documents most people handle (passports, bank letters, signed contracts, medical forms), and this tool never uploads them. Nothing is re-rendered either: pages are copied across intact, so text stays selectable and images keep the resolution your scanner produced. Your two source files are left exactly as they were and the combined document downloads as a new PDF.

Frequently asked questions

Why does the second file need to be reversed?
Because of how the paper moves. You scan the fronts, then flip the whole stack over to scan the backs, which puts the last sheet on top, so the backs come out in reverse order. Reversing that file puts them back in step with the fronts. The second file you add is set to reverse for you; untick it if your scanner already gave you the backs in order.
What if my two files have different numbers of pages?
That works. Pages alternate for as long as both files have them, then whatever is left over is added at the end rather than thrown away. This happens routinely with an odd number of sheets, where the last back is blank and often not scanned at all.
How is this different from merging?
Merge concatenates: all of the first document, then all of the second. Interleave alternates: one page from each, in turn. For two halves of the same scan, merging gives you a document that is complete but in entirely the wrong order, and it looks plausible enough that people send it before noticing.
Can I interleave more than two files?
Yes. Pages are taken from each document in turn, in the order the files are listed, so three files give you A1, B1, C1, A2, B2, C2 and so on. Use the arrows beside each file to change that order.
Are my scans uploaded?
No. The pages are recombined in your browser and the file never leaves your device. Reassembly is just copying pages between two documents already open in your tab; a server would add nothing except a copy of your scan that you could never take back. Your browser's network log records nothing during a run.

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