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Interleave PDF front and back pages

Reassemble a document scanned in two passes: one PDF of front pages and another of backs. Ordinary merging places the whole first file before the second. Interleaving takes one page from each in turn, restoring reading order without moving every page manually. The files are processed locally, so you can correct the sequence without scanning the paper again.

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Choose two PDFs: fronts first, backs second. Check their order in the preview.

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Recommended size: up to 100 MB

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How does this tool work?

Reassemble a document scanned in two passes: one PDF of front pages and another of backs. Ordinary merging places the whole first file before the second. Interleaving takes one page from each in turn, restoring reading order without moving every page manually. The files are processed locally, so you can correct the sequence without scanning the paper again.

Choose exactly two PDFs: fronts first, backs second. Their names identify the sources, while the page preview shows the interleaved result rather than merely the input files. Reimport the files in the correct order if they were selected the other way round.

Turning a paper stack over can leave the back scan in reverse order. The reversal option changes only the second file's page sequence. It does not rotate page images. Check the beginning and end of the preview before downloading.

If the page counts differ, a warning appears. Unmatched pages are kept at the end in the chosen sequence, without automatically inserting blanks. You can deselect output pages in the grid, but do so deliberately: an unexpected extra page may reveal a missed scan.

Pages are copied without systematically rendering them as images. Document-level bookmarks, interactive forms and digital signatures still need checking. Recomposition does not preserve the validity of a cryptographic signature; keep the signed originals.

How to use this tool

  1. Import fronts and backs

    Choose the front PDF followed by the back PDF.

  2. Fix the order of the backs

    Reverse the back-page order if that scan starts with the last sheet.

  3. Check and download

    Inspect the final sequence, extra pages and selection, then download.

Use cases

Scanner without duplex

Combine the two passes of a feeder scanner that only scans one side at a time.

Flipped stack of backs

Restore backs scanned from the last sheet to the first by using the reverse option.

Interleaved appendices

Alternate the pages of a file with the answers or appendices that match them one by one.

Examples

Three fronts and two backs

A3 has no matching back, remains at the end and triggers a page-count warning.

Input

Fronts A1, A2, A3; backs B2, B1, with reversal enabled.

Result

A1, B1, A2, B2, A3.

Tips and best practices

  • Use visible page numbers to confirm the first matching pair.
  • Reversing a sequence and rotating its pages are different operations.
  • Keep both source files until the result has been checked.

Frequently asked questions

Is this the same as ordinary merging?

No. A normal merge concatenates files. Interleaving alternates between them.

Does reversal turn the images upside down?

No. It reverses the second PDF's page order. Use page rotation to change orientation.

Are unmatched pages deleted?

No. They remain at the end. Check whether a missing scan caused the mismatch.

Can I alternate more than two files?

This workflow handles one front/back pair. Use merging and page reordering for a free-form assembly.

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