Alternate & Mix PDFs — Interleave Pages from Two or More Files
Combine 2 or more PDFs by interleaving their pages round-robin — perfect for merging duplex scans where odd and even pages were scanned in separate passes. Optionally reverse every other input for back-to-front scanner stacks. Free, in-browser, and no signup — your files stay on your device.
Free • No signup • Secure
How to use alternate & mix pdfs — interleave pages from two or more files
Pick your PDF files
Click to choose two or more PDFs from your computer. The files stay on your device — there is no server upload.
Optionally enable reverse-every-other
If your inputs come from a single-sided scanner doing duplex via flip-the-stack — odd pages scanned front-to-back, even pages scanned back-to-front — enable "Reverse every other input." The tool flips the even-numbered inputs internally so the interleaved output ends up in natural reading order.
Interleave round-robin
USA Sky PDF takes the first page from each input in order, then the second page from each, and so on. Output is A1, B1, C1, A2, B2, C2, A3, B3, C3… until every input is exhausted. Inputs with fewer pages simply drop out when they run dry.
Download the merged PDF
Click Alternate & Mix to save the new .pdf to your device. The original files are untouched.
Why use USA Sky PDF
Your files stay on your device
Nothing is uploaded. The interleave runs entirely in your browser, and the new file is saved straight to your downloads folder.
Duplex-scanner-friendly reverse mode
The reverse-every-other-input flag is the exact transform needed to rebuild a duplex scan from a single-sided scanner that has to flip the stack mid-job. Without this, the even pages come out in the wrong order.
Form fields carry through
AcroForm widgets on each copied page survive the round-robin. The catalog-level /AcroForm dictionary is rebuilt from the first input, so interactive form fields render normally in Acrobat Reader.
Free with no signup
No account, no email, no watermarks. There's nothing to upgrade for this tool because nothing leaves your device.
Frequently asked questions
Is alternate-mix really free?
Yes. Free with no signup and no per-conversion limit.
Do my files leave my computer?
No. The interleave runs entirely in your browser. USA Sky PDF's servers never see your PDFs for this tool.
What's the reverse-every-other option for?
Flatbed scanner duplex pattern. A typical single-sided scanner can fake duplex by having you scan the odd pages front-to-back, flip the stack, then scan the even pages back-to-front. The even-pages file is therefore in reverse order. Enable reverse-every-other and the tool flips the even-numbered inputs internally before interleaving, so the output reads naturally page 1, 2, 3, 4…
What if my inputs have different page counts?
Round-robin continues until every input is exhausted. If A has 10 pages and B has 8, you get A1, B1, A2, B2, A3, B3, A4, B4, A5, B5, A6, B6, A7, B7, A8, B8, A9, A10 — B drops out when it runs dry.
Are bookmarks and form fields preserved?
Form fields on every copied page survive (each page's /Annots carries through). The catalog-level /AcroForm dictionary and the document outline (bookmarks) are taken from the FIRST input only — combining outlines from multiple inputs would conflict. If you need a different input's bookmarks to be authoritative, list it first.
How is this different from Merge?
Merge concatenates: A1, A2, A3, B1, B2, B3, C1, C2, C3. Alternate & Mix interleaves: A1, B1, C1, A2, B2, C2, A3, B3, C3. Different operations for different use cases — merge for sequential combining, alternate for duplex scanner reconstruction or alternating-section layouts.