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Collate a double-sided scan

Most home scanners with a document feeder only scan one side. The usual trick is to scan the fronts, flip the stack over and scan the backs — which leaves you with two files: one with pages 1, 3, 5… and one with 2, 4, 6… (often in reverse order).

The tool checks that both files belong together: the fronts and backs should have the same number of pages, or one more front when the last sheet is single-sided. It's a far quicker fix than scanning everything again one sheet at a time, and it works with scans from any feeder scanner or copier.

Collate Double-sided Scan puts them back together: front 1, back 1, front 2, back 2, and so on. Tell it whether the backs came out in reverse and it handles that too. The result is a single PDF that reads like the original paper document.

Both files stay on your device: the collating runs in your browser and nothing is uploaded. If the two files have very different page counts, you get a warning before anything goes wrong.

Runs in your browser★ Only on ShamsPDF

Drop PDF files here

PDF · or click to choose · you can also paste · up to 300 MB · stays on your device

Your privacy

This tool works entirely inside your browser. Your files are never uploaded to any server.

How to use Collate Double-sided Scan

  1. 1

    Add the fronts file

    The first file is the one with the front sides (pages 1, 3, 5…).

  2. 2

    Add the backs file

    The second file holds the back sides.

  3. 3

    Say if the backs are reversed

    Tick Back pages are in reverse order if you turned the whole stack over to scan them — that's the usual case.

  4. 4

    Collate and download

    Get one PDF with every page in reading order.

Questions and answers

How do I know if my back pages are reversed?

Open the backs file: if it starts with the back of the last sheet, they're reversed. That's what happens when you flip the stack over.

What if one file has one page more?

That's fine — for example when the last sheet has nothing on the back. Larger differences are shown as an error so you can check the files.

Should blank backs be removed?

Run the result through Remove Blank Pages to drop empty backs after collating.

Are my scans uploaded?

No. Collating runs entirely in your browser.

Can it also fix the order of mixed-up scans?

For scans in a random order, use Smart Arrange, which reads page numbers and detects front/back pairs.

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