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Password protect a PDF.

Real AES-256 encryption, and your choice of what a reader may print, copy or change. It happens in your browser, so neither the document nor the password you pick is ever uploaded.

Drop a PDF hereor click to choose one — it opens inside this tab and is never uploaded

The engine is qpdf, compiled to WebAssembly and running on your own machine. Your file and your password never leave the browser — you can turn off your internet after this page loads and it still works.

Need the opposite?Remove a password, or lift printing and copying restrictions.Unlock a PDF →

How to password protect a PDF

  1. Open your PDFDrag it onto the page or choose it from your computer. It never leaves your browser.
  2. Choose the passwordThis is the password a reader is asked for before the file will open. Nobody can recover it, so save it somewhere first.
  3. Decide what readers may doPrinting at full quality, low quality or not at all, and whether copying, editing, commenting, form filling and reordering pages are allowed.
  4. Download the protected fileIt's encrypted with AES-256, and every reader that respects the standard will ask for the password.

The thinking behind it

We wrote the guides first and built the tool because we kept needing it.

Guide · 6 minHow to sign a PDF without uploading it anywhereThe documents that need signing are exactly the ones you shouldn't hand to a free converter site. Every way to sign one locally, on every platform.Guide · 6 minMove off browser-saved passwords in an hourThe browser's password box is fine until the day it isn't. Here's the migration in order, which passwords to fix first, and the one risk you're taking on.

Questions

Is the encryption real?

Yes. It's AES-256, the strongest encryption the PDF specification defines, written by qpdf — the same tool a lot of publishing pipelines use. A reader without the password cannot read the contents, and that isn't a policy, it's mathematics.

Is my file uploaded?

No. qpdf is compiled to WebAssembly and runs inside your browser, so the document and the password you choose never reach a server. You can turn your internet off after the page loads and it still works.

What happens if I lose the password?

The file is gone. Not difficult, not slow — gone. Nobody can recover it, including us, because there is nothing to recover from: we never had the file or the password. Put it in a password manager before you download.

What's the difference between the two passwords?

The one you type first is the open password: without it the file won't open. The optional owner password controls the permissions instead — printing, copying, editing. Set them differently and readers can open the document but can't change what they're allowed to do with it. Leave the owner password blank and it reuses the first one.

Are the permissions actually enforced?

The encryption is enforced by mathematics; the permissions are enforced by convention. Every mainstream reader — Preview, Acrobat, Chrome, Edge — obeys them, but someone with the open password and the right tool can ignore them. Use permissions to state intent, not to make something impossible.

Why can't I choose 128-bit for older readers?

Because the 40-bit and 128-bit PDF formats use RC4, which is broken, and qpdf refuses to write them without an explicit override. Offering the weak option only helps someone accidentally pick it. Every reader from the last decade handles AES-256.

Can I protect a PDF that's already protected?

Not directly — a PDF carries one set of encryption, so the old one has to come off first. Take it off with the unlock tool, then come back here.

Does it change the document itself?

No. The pages, text, images, fonts and form fields are copied through exactly as they were. The only difference is the encryption wrapped around them.