How many PDFs can I merge at once?

There's no hard cap — the limit is your browser's RAM. In practice, merging up to about ~50 MB of combined PDF data works smoothly on most laptops. Beyond that you may see slowdowns during reordering. Each individual source PDF caps at 10 MB on the free tier (the v1.1 paid tier lifts that to 200 MB).

Do annotations and form fields survive the merge?

Yes. pdf-lib preserves the page object tree from each source — annotations, AcroForm fields, embedded fonts, and bookmarks all carry over to the merged output. If two source PDFs have form fields with the same name, the merged output keeps both as independent fields (this is correct PDF behaviour, not a bug).

Can I merge password-protected PDFs?

Not in the free tier — encrypted PDFs need to be unlocked first, and password removal requires server-side compute that the browser can't do (the cryptography spec for it is too heavy for a JS implementation to be practical). The v1.1 paid tier adds an unlock step ($1.99/document) before the merge.

Does the merged file get uploaded anywhere?

No. The merge is performed by pdf-lib in your browser tab using the source bytes you dropped — there is no upload step in the code path. We cannot leak what we never receive. Verify by opening DevTools' Network tab while you merge: zero outbound requests carrying any of your PDFs.

Can I split, then re-merge later?

Yes — that's a common workflow. Use Split & Extract to pull specific page ranges out of a long source PDF, edit / sign / annotate those pages individually, then merge them back together (along with any new pages) into a final output. All operations are non-destructive on the original file you dropped — that source is held in browser memory, never overwritten.

Do my files leave my browser?

No — at all, today. All editing runs client-side via pdf.js and pdf-lib. The v1.1 paid tier will add opt-in cloud OCR / unlock; even then files are deleted within 60 seconds.

Yes. Everything in the editor today (annotations, AcroForm fill, watermark, page numbers, split, merge, export) is free forever. Paid tier ($1.99/document) covers cloud OCR + AI autofill on scanned PDFs in v1.1.

How do I keep my work between sessions?

Edits autosave to your browser's IndexedDB every 500 ms. The editor URL becomes /app?s=… — copy or bookmark to return. Sessions live entirely on your device.

Can I use this for sensitive documents — tax, medical, legal?

Yes — that's the point of client-side execution. Your tax return, medical record, or legal contract literally never touches our infrastructure. Verify in DevTools' Network tab.

Does Vietnamese text export correctly?

Yes. The export pipeline auto-fetches Roboto-Vietnamese (with full diacritic coverage) when any annotation contains non-ASCII text.

Merge PDF · drag to reorder

Merge PDFs — drag, drop, download.

Drop multiple PDFs and combine them into one. Reorder by dragging tiles, then click merge — no upload, no signup, no quality loss.

✓ Stays in browser
✓ No signup
✓ Lossless

Want to edit more on this PDF?

Sign, redact, watermark, autofill · stays in your browser

Open the free editor How it works

PDF

Drop multiple PDFs

or click to browse — stays in your browser

Output filenameInsert blank page between files.Adds a separator A4 page where one file ends and the next begins.Add bookmarks (one per file).Each source file gets a top-level outline entry pointing at its first page.

Drop multiple PDFs

Four steps · seconds

How it works.

Step 01
Drop the PDFs
Drag multiple PDFs onto the dropzone or click to multi-select. The files stay in your browser.
Step 02
Reorder
Drag tiles to set the page-sequence in the merged output. Pages from the first tile come first.
Step 03
Merge
We copy every page from every input into a fresh output document — no re-rendering, no quality loss.
Step 04
Download
The merged PDF saves locally. Originals are untouched; merge again with different ordering if needed.

Common questions

About merging PDFs.

How many PDFs can I merge?

No hard cap below browser RAM. We comfortably handle 50+ files. If a single combined output exceeds ~200 MB, expect the browser to slow down during the save step.

Will quality degrade?

No. We copy the original page streams byte-for-byte into the output. Text, vectors, fonts, and embedded images are preserved exactly.

What about bookmarks, form fields, signatures?

Form fields and bookmarks survive on a per-page basis. Document-level digital signatures applied BEFORE merging are invalidated (the bytes change). Sign AFTER merging.

Can I merge an encrypted PDF?

Not directly — encrypted PDFs need to be unlocked first. Run /tools/unlock-pdf, then merge the unlocked file.

Will my files upload anywhere?

No. Open DevTools → Network and you'll see exactly zero outbound requests when you click Merge. Everything runs client-side in your browser.

Keep going

Need to do more than this?

Open the full editor for signing, redaction, watermarks, autofill, and the rest of the toolbelt — same file, no upload, no signup.

Open the free editor

Merge PDFs — drag, drop, download.

Want to edit more on this PDF?

How it works.

Drop the PDFs

Reorder

Merge

Download

About merging PDFs.

Related tools.

Split PDF →

Rotate PDF pages →

Delete pages →

Extract pages →

Need to do more than this?