Alternate merge
Interleave two PDFs, one page from each in turn.
Alternate merge weaves the pages of two PDFs together — page 1 from the first, page 1 from the second, page 2 from the first, and so on — commonly used to recombine separately-scanned front and back sides of a double-sided document.
Click to choose a PDF, or drag one in here
One file
Click to choose a PDF, or drag one in here
One file
How to use
- Upload the two PDFs you want to interleave.
- If the second PDF was scanned back-to-front (common when scanning double-sided pages one side at a time), check the reverse option.
- Click "Interleave & download" to get pages in order: A1, B1, A2, B2, ...
Common use scenarios
- Recombining a document scanned as two separate files — one for front sides, one for back sides.
- Interleaving two related documents, like a set of questions and a matching set of answer sheets.
- Combining alternating content from two sources without manually reordering pages.
- Reconstructing a duplex document from a scanner that can only scan one side at a time.
✓Content & verification reviewed: 2026-09-17
How we verify Alternate merge
How to confirm the pages interleaved correctly.
Reversing the second file matters for duplex scans
A scanner that flips the stack to scan the backs often produces them in reverse order — check the "reverse second PDF" option so backs line up with the correct fronts.
Different page counts are handled by appending
If the two files don't have the same number of pages, the extra pages from the longer file are added at the end after interleaving stops.
Order alternates strictly one-for-one
The result is always A1, B1, A2, B2, ... — there's no option for a different ratio, like two pages from one file per one from the other.
Before you rely on the result
- You've identified which file is the fronts and which is the backs (or which order you want them in).
- You've checked whether the backs need to be reversed before interleaving.
- You've spot-checked the first several pages of the output to confirm the sequence is correct.
Who this is for
- Anyone reconstructing a duplex-scanned document from separate front/back files.
- People combining paired documents like questions and answers into one sequence.
- Anyone who needs to interleave two PDFs' pages without manual reordering.
Real-world examples
Reassembling a duplex scan
A single-sided scanner produces one PDF of front pages and, after flipping the stack, one PDF of back pages in reverse order — alternate merge with the reverse option puts them back in correct reading order.
Pairing questions with answers
A teacher has a PDF of exam questions and a separate PDF of matching answer keys, and interleaves them so each question is followed immediately by its answer.
Limitations
- If the two files have different page counts, extra pages from the longer file are appended at the end.
Frequently asked questions
What if my two PDFs have different page counts?
Interleaving continues until the shorter file runs out, then the remaining pages of the longer file are appended at the end.
Why would I reverse the second file?
Scanners that flip a stack of paper to scan the backs typically produce those pages in reverse order — reversing corrects this before interleaving.
Can I choose a different interleave ratio, like 2-to-1?
No, this tool always alternates one page from each file at a time.
🔒 Runs in your browser — nothing is uploaded. Results are for reference only; see the disclaimer. Last updated: 2026-09-17
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