CalcaTools

Merge PDF

A free tool to merge multiple PDF files into a single document. Drag files to reorder them, then combine with one click. All processing happens in your browser — your documents are never uploaded to any server.

Last updated: June 2026 · Free · No sign-up required

upload_file

Drag & drop PDF files here

or browse files · Select multiple PDFs

Frequently Asked Questions

How do I reorder PDF files before merging?

After adding your files, you can drag and drop them by the handles in the list to arrange them in the exact order you want them merged.

Is there a limit on the number or size of PDF files?

Since processing happens locally in your browser, the limit depends on your computer's memory. Merging a reasonable number of PDFs (e.g. 10-20 files or up to 100MB combined) runs smoothly on most modern devices.

Are my confidential PDF documents uploaded online?

No. The merging process uses pdf-lib to read and assemble pages entirely client-side. Your private documents never touch our servers.

Quick reference

StepAction
1Drop two or more PDF files
2Drag to set the page order
3Merge & download the single PDF

Interpretation guide

Use caseTip
Contract + annexesMain document first, exhibits in order
Scanned chaptersName files 01, 02… before dropping
Application packsCV + certificates + portfolio in one file

Formula & methodology

Formula: Output PDF = concatenation of all pages from each input, in your chosen order

  1. Add your PDFs — they’re processed locally with a JavaScript PDF library; nothing uploads.
  2. Reorder the files as needed.
  3. The pages are copied into one new document, preserving size and orientation, ready to download.

Worked example: a 12-page report + 3-page appendix + 1-page cover merge into a single 16-page PDF in seconds — with the cover dragged to position one before merging.

Frequently asked questions

Are my PDFs uploaded to a server?
No — merging happens inside your browser with a JavaScript PDF engine. Contracts and private documents never leave your machine, unlike most "free PDF merge" sites.
Is there a file size or count limit?
Only your device’s memory — dozens of files and hundreds of pages merge fine on a typical laptop. Very large scans (500+ MB) may be slow; split the job if so.
Will formatting or quality change?
No — pages are copied verbatim: vector text stays vector, images keep their resolution, page sizes and orientations are preserved exactly.
Can I reorder pages, not just files?
This tool orders at the file level. For page-level surgery, split first (or merge then rearrange in a PDF editor) — file-level ordering covers the common cases.
Do password-protected PDFs merge?
Encrypted files must be unlocked first — the engine can’t read protected pages without the password. Remove protection in your PDF reader, then merge.