How many PDFs can I combine at once?

As many as your device has memory for. Nothing is uploaded, so there is no per-file size cap and no queue, the practical limit is how much RAM the browser is willing to hand a single tab, which on an ordinary laptop is dozens of large documents.

What do the two toggles do?

“Add page numbers” stamps a single continuous count across the whole merged file, so the numbering runs straight through instead of restarting at each source document. “Flatten form fields” bakes filled-in form values into the page as static content, which is worth doing before you send a completed pack to someone who should not be able to change the answers.

Merge PDF

No upload · runs in your browser

Drop PDFs to mergeAdd two or more files. Reorder them nextSelect files No upload · processed locally · auto-deleted

How it works

How to merge PDF files without uploading them

Merging PDFs with FernPDF takes three steps: drop your files into the workspace, drag the cards into the order you want, and click Merge PDF. The combined document downloads instantly.

Unlike most online merge tools, FernPDF never transmits your documents. The entire operation runs in this browser tab with pdf-lib, so confidential contracts, financials, and personal records stay on your machine.

That makes it safe for legal, finance, and healthcare workflows where uploading files to a third-party server isn’t an option. It’s also faster, because there’s no upload to wait for.

FAQ

Drag any file card. The number badge on it is that file's position in the finished document.

Keep going

Split PDF

Compress PDF

Organize pages

PDF to Word

Guides for this tool

combine multiple PDFs into one file on Mac combine multiple PDFs into one file on Windows combine multiple PDFs into one file on iPhone combine multiple PDFs into one file on Android combine multiple PDFs into one file on Chromebook combine multiple PDFs into one file on Linux merge PDFs into one file for printing add page numbers to a PDF