PDF Interleave

Alternate two PDFs with reverse-order controls, an explicit remainder policy and a downloadable page map.

Put scanner fronts and backs into one alternating PDF. Reverse either stack and choose how unequal counts are handled. Your files stay on this device.

Choose source PDF A

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Choose source PDF B

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Reverse source AReverse source B

Start with source

Unequal page counts

Each PDF: 25 MiB maximum. Combined input: 40 MiB. Output: at most 300 pages / 50 MiB. Encrypted, damaged, annotated, linked, signed/form PDFs and unsupported geometry are refused. This is not sanitization; bookmarks, tags, attachments and logical page labels do not transfer.

This tool runs entirely in your browser. Your data is never uploaded, never stored, and never leaves your device.

Alternate pages from two local PDFs with independent reverse-order controls, an explicit unequal-count policy and a complete source-page map.

How to use it

1Choose the front and back PDFs as sources A and B.
2Review the start source, reversal options and remaining-page policy.
3Create the PDF, check the page map and inspect the downloaded copy.

Example

Input: A: A1, A2, A3 B: B1, B2 Start A; reverse B; append remainder
Output: A1, B2, A2, B1, A3 5 output pages; no source page discarded

Source labels refer to physical positions within each original PDF, not printed page labels.

What happens to your data

PDF reading and assembly happen locally without document upload. The new copy does not transfer every document-level feature; unsupported interactive/signed files are refused.

Last updated October 2026

Restore reading order when a single-sided scanner produces one PDF of document fronts and another of backs. This PDF interleaver takes one page from each source in turn, with independent reverse-order controls for the common case where the back stack was scanned last-page first. The result is one newly assembled PDF and a downloadable map showing where every output page came from.

This is not ordinary PDF merging. A merge places all of A before all of B; interleaving produces A1, B1, A2, B2 and continues until both inputs are exhausted. Start with B when that reflects your intended physical order. Pages are copied as supported PDF page content rather than deliberately turned into screenshots.

How it works

Choose source PDF A and source PDF B, review the start source and reverse choices, then select Create interleaved PDF. Reverse A or Reverse B changes the order within that source before alternation. For A containing A1,A2,A3 and B containing B1,B2, the default output is A1,B1,A2,B2,A3. Reversing B changes it to A1,B2,A2,B1,A3. The page map retains the original physical source positions, not a guessed printed page number.

Unequal stacks need a deliberate policy. Append remaining pages keeps every source page exactly once and places unmatched pages at the end in that source's chosen order. Require equal page counts stops with an explanation instead. The tool does not silently drop unmatched pages or invent blank backs. If a scan missed an interior sheet, equal counts do not establish that the fronts and backs belong together; inspect the source documents and resulting page map.

Each source is limited to 25 MiB, the pair to 40 MiB, and the combined result to 300 pages and 50 MiB. Supported quarter-turn rotations, media dimensions and visible crop boxes are copied with each page. There is no automatic rotation correction, scanner deskew, OCR, page-content alignment, compression or duplex-print setting. PDF page positions start at 1 and can differ from Roman numerals, bookmarks or numbers printed on a page.

Password-protected or damaged PDFs, detected forms/signature or certification structures, annotations or links, page actions, non-standard UserUnit scales and unsupported geometry are refused. Export an ordinary unsigned copy from its source application when appropriate and retain the original. The new document does not promise to carry over bookmarks, attachments, accessibility tags, logical page labels or other document-level features. This is not a malware scanner, signature validator, redaction or sanitization service; copied page resources can retain information not visible on the page.

After assembly, review the output-to-source map before downloading. The JSON map contains output position, source A/B, original page position and displayed dimensions in PDF points. It omits source filenames and document metadata. The PDF itself contains the selected page content, so review it before sharing. Both file reading and PDF assembly stay in the current browser page; no document upload is made. Surrounding website assets and anonymous usage events can still use the network.

Changing a file or setting clears the previous download. Cancel prevents a late asynchronous result from becoming available, but a PDF library operation already running may finish its local computation before returning. Clear removes the current selections and temporary download link; a file already downloaded onto your device is not deleted. Always inspect the saved PDF in the reader and printing workflow used by its recipient.

Worked example: Repair reversed back scans

Input: A: A1, A2, A3 B: B1, B2 Start A; reverse B; append remainder
Result: A1, B2, A2, B1, A3 5 output pages; no source page discarded

Source labels refer to physical positions within each original PDF, not printed page labels.

Common use cases

Recombining separate front and back scans from a single-sided feeder
Alternating matching worksheets and answer sheets
Reviewing a source-page audit map before printing a collated copy

Frequently asked questions

How is interleaving different from merging PDFs?＋

Merging concatenates complete documents; interleaving alternates one page from each source. The exact output-to-source map makes that order explicit.

What if the back scan is backwards?＋

Enable Reverse source B when B holds the back stack. Its last page is then used first. Review your scan because the tool cannot infer which front belongs to which back.

Are extra pages lost when counts differ?＋

No. Append remaining pages retains every page exactly once. Alternatively, Require equal page counts refuses the operation.

Will signatures, links and bookmarks survive?＋

Detected signed/form structures and pages with annotations or links are refused. Document-level bookmarks, tags, attachments and logical labels are not transferred. Keep the original.