Free tool · 100% private
Protect PDF
Add a password and real AES-256 encryption to a PDF. Everything runs inside your browser: your file is never uploaded and the password is never sent, so nothing can leak. It even works offline.
Choose a PDF file or drop it here
One PDF · it stays on your device
Set a password to open this PDF
Anyone opening the PDF will need this password. Keep it safe — it is never uploaded, so if you forget it the file can't be recovered.
Advanced — restrict what readers can do
These are owner-level restrictions enforced by AES-256. They still require the password above to open the file.
Encrypting your PDF…
Working entirely on your device
🔒 Nothing is uploaded — the password and encryption stay on your device
- ✓Reading your PDF on this device
- ✓Loading the AES-256 encryption engine
- ✓Encrypting with your password
- ✓Verifying the lock & finalising
Password added & encrypted
🔑 Keep your password safe — it isn't stored anywhere and can't be recovered.
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How to password-protect a PDF (without uploading it)
Most "protect PDF" websites upload your file to their servers, encrypt it there, and send it back — which means your unprotected file, and often the password, briefly live on someone else's machine. This one is different: it does the whole job on your device, with real AES-256 encryption, and it checks its own work before handing you the file.
- 1Add your PDF. Drag it onto the box or click to pick. It loads straight into your browser's memory — nothing is sent anywhere.
- 2Set a password. Type a password to open the file and confirm it. Optionally restrict printing or copying under Advanced.
- 3Protect, verify & download. Your browser encrypts the file with AES-256, re-opens it to confirm it now refuses to open without the password, then gives you the protected PDF.
Why this is safer. Since the tool never uploads your file or password, there is no copy of either on any server to be hacked, cached, indexed, or leaked. And because it verifies the lock before download, you never get a file that only looks protected.
Frequently asked questions
Is my PDF or password uploaded to a server?
No. This tool runs 100% in your browser. Your file is read into your device's memory and encrypted locally, and the password never leaves your browser — neither the file nor the password is ever sent to any server, so there's no way for them to leak. It even works offline once the page has loaded.
What kind of encryption does it use?
Real AES-256 encryption — the strongest scheme the PDF standard supports. It's applied by a WebAssembly build of the open-source qpdf engine running on your device, so the protection is genuine, not just a viewer prompt.
Can I remove the password later?
Anyone who knows the password can open the PDF in any reader. To permanently remove it, open the file with the password and re-save an unprotected copy. Keep the password safe — if you forget it, the file can't be recovered, because nothing is stored on any server.
What if my PDF is already password-protected?
An already-encrypted PDF can't be re-encrypted without its current password. If you add one that's already protected, the tool detects it and tells you, instead of giving you a broken file.
Is it really free?
Yes — completely free, no sign-up, no watermark, no account limits. It's part of AttendFlow's free student tools.
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