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Alternate & Mix PDF
Alternate & Mix PDF interleaves pages from two or more documents: page 1 from file A, page 1 from file B, page 2 from file A, and so on. It is built for duplex scanning workflows where the front sides and back sides arrive as two separate stacks.
How to use Alternate & Mix PDF
- Add at least two PDF files — the order you add them sets the interleave order.
- Run the mix; the tool walks every document page by page until the longest file is exhausted.
- Download the single interleaved PDF.
Where Alternate & Mix PDF is useful
- Recombining front sides and back sides after a single-sided duplex scan.
- Pairing an original document with its translation page by page.
- Merging two versions of a form so each sheet carries its own counterpart.
Formats, algorithms and limits
Interleaving is page-level and round-robin: with files A and B the output reads A1, B1, A2, B2 and so on. Shorter documents simply run out first while the remaining pages of the longer file are appended in order. Pages are copied, not re-rendered.
Troubleshooting and honest limits
- Check page counts first — if the stacks are uneven the tail of the output comes from one file only.
- Rotate the back-side stack before mixing if the reverse pages are upside down.
- For strict front/back ordering, keep the two source files separate rather than merging them first.
Frequently asked questions
Does alternating mix work with three or more files?
Yes. Pages are taken in turn from each document in the order you queued them, one page at a time, until every file is exhausted.
What happens when the files have different page counts?
Interleaving stops for the shorter document and the remaining pages of the longer one are appended, so no page is ever dropped.
Can I undo a mix?
Not directly, but split the mixed file back into two documents using Split PDF with odd and even page ranges to recover the original stacks.
Will the mixed file be larger than the inputs?
It is normally close to the sum of the two files, because pages are copied with their existing compressed streams.
Related tools
Page written and reviewed by the FreeConvertio engineering team on 2026-10-14. Alternate & Mix PDF runs entirely in your browser — no uploads, no account and no daily limits.