Alternate and Mix PDF Pages
Alternate and mix PDF pages from two or more files — the first page of each, then the second of each, and so on. The classic use: your scanner did all the fronts, then all the backs, and you need them back in order.
Fit Meter
Settings appear once you add a PDF.
Advanced 1
Still going. Your own device is doing this, so a long scan or a big batch takes as long as it takes — and none of it is being uploaded.
Bytes of your files sent anywhere: 0 B · nothing leaves this tab
Every request this page makes is listed as it happens. You’ll see our own code loading, and for some formats a codec engine, but never your file going out.
- Waiting for network activity…
Check it yourself: open your browser’s developer tools on the Network tab, or turn off Wi-Fi once the page has loaded. The tools keep working.
How to alternate and mix PDF pages
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Add your PDFs
Drop the PDFs — fronts first, then backs. Use the arrows to set which file comes first.
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Check the settings
If the backs were scanned by turning the whole stack over, switch on Reverse the last file’s pages.
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Save the result
Mix. You get one PDF: front 1, back 1, front 2, back 2… When one file runs out, the rest of the other follows.
Why it doesn’t upload
Double-sided scans are usually paperwork — contracts, forms, medical records. Putting them back together here means both halves stay on your device.
Check it in your browser’s Network tabWorth knowing
- Pages are copied exactly; nothing is re-scanned or recompressed.
- If the files have different page counts, the leftover pages go at the end in order.
- Password-protected PDFs need their password removed first.
Under the hood
What happens to your file
Pages from two or more files are interleaved — A1, B1, A2, B2 — with any source reversed first, which is how a stack scanned fronts then backs becomes one document in order. Pages are copied as they are; nothing is re-scanned or recompressed.
Reference: pdf-lib documentation
Questions
How do I combine front and back scans into one PDF?
Add the fronts PDF, then the backs PDF, and press Mix pages. If the backs are in reverse order — common when you flip the stack — switch on Reverse the last file’s pages first.
What does interleaving PDF pages mean?
Taking pages alternately from two or more documents: the first page of each, then the second of each, and so on, into one file.
Can I merge odd and even pages?
Yes — that’s the same job. Put the odd pages first and the even pages second.
Can I take two pages at a time from each file?
Yes, under Advanced: set how many pages to take from each file before switching.