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Lizely

Alternate Mix PDF

Interleave two local PDFs in A1, B1, A2, B2 order and append any remaining pages without uploading either document.

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Choose non-empty PDF A and PDF B, each no larger than 25 MiB.
  2. 2.Confirm that both source files are already in the intended internal order.
  3. 3.Select Alternate and mix PDFs, verify the A+B page total, and download the result.

About Alternate Mix PDF

Alternate Mix PDF combines two local documents by interleaving their pages. Choose PDF A and PDF B, then select Alternate and mix PDFs. The output order is A1, B1, A2, B2, and so on. When one document runs out first, every remaining page from the longer document is appended in its original order. Loading, copying, serialization, and download creation happen inside the browser, with no upload to Lizely.

The ordering rule is intentionally fixed and visible. A three-page A document and a two-page B document produce A1, B1, A2, B2, A3. A one-page A document and a three-page B document produce A1, B1, B2, B3. The result line reports the page count of each input and the total output count, which must equal the sum of both inputs.

Pages are copied as PDF pages through the existing library rather than converted to screenshots. Each copied page retains its own page-box dimensions, rotation, vector drawing, text, and embedded raster content to the extent supported by the library's copy operation. The tool does not force every page to the first document's size, stretch content, rasterize text, or insert blank separator pages.

This workflow is useful for joining front and back scan streams, alternating question and answer documents, pairing translated pages with originals, combining two chronological page sets, or merging odd and even batches that are already in the correct internal order. The tool does not guess whether either input should be reversed. If a scanner produced one stack in reverse order, reorder that source with a dedicated tool before mixing it.

Each input must be a non-empty PDF no larger than 25 MiB. Encrypted, damaged, unsupported, oversized, and incorrectly labeled files produce a visible error. Password protection is not bypassed. Choosing a replacement for either input clears the old output. A job identifier prevents a slower earlier operation from replacing a result made from newer files.

The new filename combines both cleaned source names and adds -alternated.pdf. The original files remain unchanged. Interactive document behavior such as form fields, bookmarks, outline destinations, scripts, attachments, and cross-document links may not survive page copying with the same semantics, so the tool does not promise preservation of those advanced structures. Users should inspect important interactive files after mixing.

Because the entire operation runs in one browser tab, the practical memory cost can exceed the two source file sizes: both documents and the newly serialized result may coexist temporarily. The 25 MiB limit applies separately to each input, not to their combined output. Close other heavy tabs if the device is memory constrained, and keep irreplaceable originals outside the browser workflow.

The first selectable file is always A and therefore supplies the first output page. Swapping the two selections changes the sequence to B1, A1, B2, A2 under the original names. The interface does not infer front versus back scans from filenames or page content, so users retain explicit control over which stream leads.

This tool does not merge all pages of A followed by all pages of B, reverse a source, select ranges, deduplicate pages, compare content, repair broken PDFs, or create booklet signatures. Use Merge PDF for simple concatenation, Reorder PDF Pages for manual sequencing, and Booklet PDF for imposition. Use Alternate Mix PDF when the desired truth is the documented A/B alternating sequence with unmatched tail pages preserved.

Methodology & sources

Validate two bounded PDFs, load both without metadata updates, derive a deterministic A-then-B reference sequence for every shared index, append unmatched tail pages, copy each referenced page into a fresh document without resizing, verify the result count by construction, serialize once, and revoke stale output URLs.

Frequently asked questions

What is the exact output order?
Pages are copied A1, B1, A2, B2 and continue that way; remaining pages from the longer PDF are appended.
Does the tool reverse either PDF?
No. Both inputs keep their existing internal order.
Are pages resized to match?
No. Each copied page keeps its own PDF page box and is not stretched to another page size.
Are the PDFs uploaded?
No. Both files are loaded, copied, combined, and saved locally in the browser.

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