PDF tools · merge variant
Two files, one document: the fronts in one, the backs in the other. Interleave deals them back together a page at a time. It is the one merge variant the careful scanners keep behind a meter elsewhere; here it is a tray and a button. The plain merge is on the Merge PDF page.
For a two-sided document scanned on a one-sided scanner: the fronts in one file, the backs in another, dealt back into order.
Pick the two files
Set the dealing order
Interleave and download
First file (A)
the fronts · drop it here, or click
Second file (B)
the backs · drop it here, or click
When in doubt, leave B in its own order and check page 2 of the result: if it is the document's last back page instead of its first, the backs ran in reverse and the box is the fix.
Pick both PDFs to begin.
The page copies one page from A, one from B, one from A, and so on into a new file, with B's order reversed when you ask. Pages are copied, not rebuilt, so nothing is recompressed; the engine is the same page-copying the merge tool measured at 71 milliseconds for a 25-file pack.
A missing or doubled page in either scan throws the whole deal out from that point on; this page deals numbers, it does not proofread. Split a wrong pair out with the Split PDF page and deal again. If one file is longer, its extra pages land at the end, and the result line says so.
A password-protected PDF cannot be opened by this tool. Take its password off first with the unlock tool, then bring the file back.
The classic one: a two-sided document scanned on a one-sided scanner. You scan the fronts in order (file A), flip the stack, and scan the backs (file B), which the scanner takes last-page-first. Interleave deals them back together: A1, B1, A2, B2, with B read back to front when you tick the box.
The shorter file deals in until it runs out; the longer file's remaining pages follow at the end, in their own order. The result line says so, so an odd page count never hides.
No. This page deals pages like cards, by number; it cannot tell a front from a back. Check the merged order on a few pages before you rely on it, especially the first pair, which tells you whether the backs ran in reverse.
Nowhere. They are read into this page and interleaved in your browser. Watch the network panel while it works if you want to check.