Alternate & Mix
Combine two PDFs by alternating their pages — perfect for merging separate odd/even scans.
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Single-sided scanners create a familiar headache. You scan a double-sided stack once for the front faces, flip it, and scan again for the backs, and now you own two PDFs: one with all the odd pages, one with all the evens. PDFora's alternate and mix tool weaves them back together, taking page 1 from file A, page 1 from file B, page 2 from A, page 2 from B, until the document reads in its original order.
The interleaving runs entirely in your browser. Neither PDF is uploaded, so scanned bank statements, medical records, or signed agreements are collated on your own machine and nowhere else. The tool is free, asks for no email address, prints no watermark on the result, and lets you mix as many pairs of files as your day requires.
Reordering pages by hand is the alternative, and for a 60-page scan that means 30 careful drag-and-drop moves with plenty of chances to slip. Alternate mixing does the job in one pass, every time, without a miscount.
How to alternate and mix two PDFs online
- Open the Alternate & Mix tool on getpdfora.com. Both files will be processed locally in your browser.
- Add the first PDF, typically the odd pages or front sides of your scanned stack.
- Add the second PDF, typically the even pages or back sides.
- Check the order: the merged file starts with page 1 of the first document, so put the sheet that should open the document in slot one.
- Click Mix. The tool interleaves the two files page by page into a single PDF.
- Preview the result to confirm the sequence reads correctly, then download it.
When to use this tool
- Collating scanned pages from a duplex document captured on a single-sided office scanner, the classic odd-and-even merge.
- Rebuilding a two-sided signed contract after the fronts and backs were scanned as separate passes.
- Interleaving a translated document with its original so each English page is followed by its Spanish counterpart for side-by-side review.
- Combining question pages with their answer pages so an exam reads question, solution, question, solution.
- Merging front-of-card and back-of-card scans of an index card archive into one browsable file.
- Restoring a double-sided medical intake packet that a clinic scanner split into two halves.
Tips for the best results
- Many single-sided scanners capture the flipped stack in reverse, so the even-page file may run backwards. Reverse its page order first, then mix.
- Do a quick sanity check before mixing: both files should have the same page count, or differ by exactly one if the last sheet was blank on the back.
- After downloading, read the first four pages. If they run 1, 2, 3, 4 the mix is right; if not, swap which file goes first and run it again.
- Remove blank backs from the even-page scan beforehand, otherwise empty pages land between every pair of printed ones.
- Name your scans something like report-odd.pdf and report-even.pdf at scan time so you never guess which half is which.
Frequently asked questions
What is alternate and mix in PDF terms?
It is a merge that interleaves rather than appends: page 1 of document A, then page 1 of document B, then page 2 of A, and so on. Standard merging would put all of A before all of B, which is the wrong order for collating scanned pages.
Why are my scanned odd and even pages in separate files?
Single-sided scanners can only read one face per pass, so double-sided documents are scanned twice, once per side. Each pass produces its own PDF, and the alternate mix tool exists precisely to zip those two halves back together.
My merged file reads 1, 3, 2, 5, 4. What went wrong?
Your second file was almost certainly scanned in reverse order, which happens when the flipped stack feeds last-sheet-first. Reverse the page order of the even file, then run the mix again.
Are my documents kept private?
Yes. Both PDFs are read and combined locally in your browser, and nothing is transmitted to any server. Close the tab and no copy exists anywhere except the file you downloaded.
Do the two PDFs need identical page counts?
The counts should match, or differ by one when the final back side was blank. A larger mismatch usually means the scanner skipped or double-fed a sheet, and it is worth rescanning before you mix.
Is there a charge or a watermark?
No on both counts. The tool is free, needs no signup, adds nothing to your pages, and there is no ceiling on how many documents you can collate.