Is there a limit on file size or number of PDFs?

No hard limit is enforced, but very large files or long lists are processed on your device's CPU, so performance depends on your hardware.

Can I reorder pages within a single file, not just the file order?

Not currently — this merges whole files in the order you set; page-level reordering within a single PDF isn't supported yet.

It's rejected with a clear error message rather than silently failing or corrupting the output — remove or unlock it before merging.

No — pages are copied as-is; merging doesn't re-render, recompress, or otherwise alter page content.

Documents

Combine multiple PDF files into one.

🔒 Runs entirely in your browser — nothing here is ever uploaded

Combines multiple PDF files into a single document, in the order you choose, entirely in your browser.

How to use it

Formula

Uses pdf-lib, an open-source PDF library, to copy every page from each source file into one new PDF in your chosen order — no server involved.

Worked example

A 3-page PDF and a 5-page PDF merge into one 8-page PDF, in whichever file order you set.

Recommendations

• Reorder files before merging — the output follows the list order top to bottom, and re-merging after download means starting over.
• Password-protected or corrupted PDFs will be rejected with an error rather than silently producing a broken file.
• For very large files, merging happens on your device's CPU, so expect it to take a few seconds longer than a small file.

Frequently asked questions

No — merging happens entirely in your browser using a local PDF library; your documents never leave your device.

Related tools

Sources