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Alternate & Mix PDF
Interleave the pages of two PDFs — page 1 of the first, page 1 of the second, and so on. Perfect for joining separately scanned front and back sides. Runs in your browser.
First PDF (odd pages / fronts)
Second PDF (even pages / backs)
About Alternate & Mix PDF
Alternate & Mix takes two PDFs and weaves their pages together: page 1 of the first file, then page 1 of the second, then page 2 of the first, and so on. If one file is longer, its remaining pages are added at the end.
The classic reason to need this is a scanner without double-sided (duplex) scanning. You feed a stack of two-sided paper through once to capture every front, flip the stack over and feed it again to capture every back. You end up with two PDFs — all the odd pages in one, all the even pages in the other — and the second pass usually arrives in reverse, because flipping the stack puts the last sheet on top. Ticking “Reverse the second file” corrects that, so the backs line up with their fronts.
It is just as useful for documents that were never scanned. Pair a set of slides with a page of speaker notes after each one, alternate a question paper with its answer sheet, or put an English page beside its translation for side-by-side review. Plain merging would put one whole file after the other; alternating keeps each pair next to each other.
Pages are copied, not re-rendered, so text stays selectable and images keep their original quality. Both files are processed inside your browser and never uploaded.
How to alternate and mix two PDFs
- Add the PDF with the first page of each pair — for scans, the file with all the front sides.
- Add the second PDF — for scans, the file with all the back sides.
- If the backs were scanned in reverse, tick “Reverse the second file”.
- Use “Swap order” if the files went into the wrong slots.
- Click Mix & download to get one interleaved PDF.
Tips & common problems
Check one sheet before trusting the rest
Open the result and compare pages 1 and 2 with the paper original. If page 2 shows the back of the last sheet, the second file needs reversing — run it again with the box ticked.
Blank backs still count
If some sheets were single-sided, the scanner still captured a blank back for them. Leave those blanks in until after mixing, then remove them with Remove Pages — taking them out first throws every later pair out of step.
Page counts do not have to match
When one file is longer, its extra pages are appended at the end in order. Nothing is dropped.
Unlock protected files first
A PDF with an open password cannot be read until it is unlocked. Use Unlock PDF, then mix the unlocked copy.
Frequently asked questions
What does alternate and mix mean for a PDF?
It interleaves two documents page by page — A1, B1, A2, B2 and so on — instead of putting one whole file after the other like a normal merge.
How do I combine separately scanned front and back pages?
Add the fronts as the first file and the backs as the second, tick “Reverse the second file” if the backs came out last-page-first, and download. The pages come out in reading order.
What if the two PDFs have different numbers of pages?
Pages are paired for as long as both files have them; the remaining pages of the longer file are added at the end.
Can I mix more than two PDFs?
This tool pairs two at a time. To weave in a third, mix the first two, then mix the result with the third file.
Are my files uploaded?
No. Both PDFs are read and combined inside your browser, and nothing is sent to a server.