Interleave PDF Pages (Collate Scans)
Put single-sided scans of a double-sided document back in order.
How are the pages split up?
Files
Final page order
Your PDF is ready
About the Interleave PDF Pages (Collate Scans)
A single-sided scanner turns a double-sided document into two piles of pages: all the fronts, then all the backs — and because you turn the stack over to scan the backs, they usually come out last page first. Interleave PDF Pages puts them back together as front 1, back 1, front 2, back 2 …, reversing the backs for you. It also works when the scanner saved everything in one file (fronts first, then backs), and it can alternate pages from any number of PDFs — A1, B1, C1, A2, B2 … — one or several pages at a time.
The final page order is shown as thumbnails before anything is saved, with each page labelled (Front 3, Back 3, B2 …), so a wrong order is easy to spot. When one file has fewer pages, the others carry on, or blank pages keep every file in step. Pages are copied exactly as they are — no re-compression — and links between pages, bookmarks and form fields keep working. Everything happens in your browser; your files are never uploaded.
How to use it
- Choose how the pages are split up: Front and back scans (2 files), One file: fronts, then backs, or Alternate several files.
- Add the PDF files. For front and back scans, the first file must hold the fronts — use Swap first two or the arrows if they are the wrong way round.
- Tick Reverse page order for any file that runs last page first (back sides scanned by turning the stack over usually do; it is ticked for them by default).
- Check the Final page order thumbnails, then press Make PDF and download the collated file.
Examples
fronts.pdf (pages 1–10) + backs.pdf (scanned from sheet 10 back to sheet 1), backs reversed
20 pages: front 1, back 1, front 2, back 2 … front 10, back 10
scan.pdf with 8 pages: 4 fronts, then the 4 backs last page first
Page order 1, 8, 2, 7, 3, 6, 4, 5
A (2 pages), B (3 pages), C (1 page), one page at a time
A1, B1, C1, A2, B2, B3 — or A1, B1, C1, A2, B2, blank, blank, B3, blank with blank pages
A (4 pages) and B (2 pages), 2 pages from each file at a time
A1, A2, B1, B2, A3, A4
Common uses
- Scanning double-sided contracts, bank papers, report cards or forms on a scanner that only scans one side.
- Fixing a phone-scanner app export where all the back pages ended up after the fronts.
- Putting translation and original pages side by side in reading order (original 1, translation 1, …).
- Alternating question and answer sheets, or slides and note pages, from two files.
Why the backs come out in reverse
After the fronts are scanned, the stack is turned over and fed again. The sheet that was last is now on top, so the scanner reads the back of the last sheet first: the backs file runs from back 10 to back 1. Reverse page order turns it round before the pages are interleaved. If your scanner or app already saved the backs in the right order, untick it — the thumbnails show at once which way is right.
When the page counts differ
If a back side was blank and not scanned, or a page was fed twice, the two files don’t have the same number of pages and the page shows a warning. Carry on with the other files simply continues with the pages that are left. Add blank pages to keep them in step puts a blank page (the same size as the page it stands in for) wherever a file has run out — useful when the result is printed double-sided again. In one-file mode, type the number of front sides if the first half isn’t right.
What is kept
Pages are copied exactly as they are — text, images, page size and rotation — without re-compressing anything. Links from one page to another keep pointing at the right page after the reordering, each file’s bookmarks are kept (optional), and form fields stay fillable. Not carried over: accessibility tags, file attachments, document-level scripts and page labels. A digital signature can’t stay valid in a rearranged file, so its visible appearance is kept and the signature data removed.
Limitations
- Encrypted or password-protected PDFs must be unlocked first with Unlock PDF.
- The preview shows the first 300 pages of the new order; the saved file has them all (up to 100,000 pages).
- Pages keep their own size and rotation — to make them all the same size afterwards, use Resize PDF Pages.
- The first use downloads the PDF engine once, so it needs an internet connection.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
Are my files uploaded?
No. The PDFs are read and combined by your browser on your device; nothing is sent to MySmartCoPilot or anyone else.
How do I scan double-sided pages with a single-sided scanner?
Scan the stack once for the front sides and save it as one PDF, turn the whole stack over and scan the back sides into a second PDF. Add both here with Front and back scans, keep Reverse page order ticked for the backs, and download the collated file.
What is the difference between interleaving and merging?
Merging puts whole files one after the other (all of A, then all of B). Interleaving takes pages from the files in turn (A1, B1, A2, B2 …). To join files end to end, use Merge PDF.
My backs are in the wrong place — what should I change?
Look at the thumbnails: if back 1 shows the back of the last sheet, the backs are reversed the wrong way — untick or tick Reverse page order for the backs file. If every page is one off, a page is missing or doubled in one file; remove it first (for example with the PDF Page Extractor) and try again.
Can I interleave more than two PDFs?
Yes. Choose Alternate several files, add the files in the order you want, and set how many pages to take from each file at a time.