Security
Password-protect a PDF
Add a password and strong AES encryption to any PDF, so only people with the password can open it. Everything happens in your browser — your file and password never leave your device.
Part of the all-in-one 4PDFs toolkit. Premium tools unlock with a one-time $6.99 Day Pass.
Drop your PDF here or browse
.pdf — in your browser, nothing uploaded
AES-256. Runs locally · Nothing uploaded.
How to password-protect a PDF
Add your PDF
Drop in the document you want to keep private.
Set a password
Choose a strong password — only people who have it can open the file.
Download the protected PDF
Share an encrypted file that prompts for your password to open.
Why use 4PDFs
- Strong AES-256 encryption
- Sets an open password on the file
- Runs 100% in your browser — private by design
- Great for contracts, statements and IDs
- Your password is never sent anywhere
- No watermarks on your PDF
Frequently asked questions
Is protecting a PDF free?
You can load any PDF for free. Downloading the encrypted file is included with the $6.99 Day Pass — 24 hours of unlimited use, no subscription.
What encryption is used?
Industry-standard 256-bit AES, applied right in your browser by qpdf (compiled to WebAssembly). The password actually encrypts the file's contents.
What if I forget the password?
Keep it somewhere safe — for security there's no recovery or backdoor. A password you set is the only way to open the file.
Is my file private?
Completely. The encryption runs entirely inside your browser — your PDF and your password are never uploaded to a server.
Protect your PDF now
Every premium PDF tool for 24 hours. $6.99 — one charge, no subscription.
Get the Day Pass →