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PDF Password Protect

Lock a PDF behind a password with AES-256 encryption, free. The locked file can be unlocked again with the same password in this tool. Your file never leaves your browser.

Lock or unlock a PDF

Choose a file, set a password, and download the locked copy. Use Unlock mode to open a file locked here before.

Drop PDF file here
or click to browse
Heads up: this uses AES-256 file encryption, not the built-in password feature of Adobe PDF. Files locked here open with this tool (or any AES-GCM decryptor), not directly in Adobe Reader.
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How locking works

Your PDF is encrypted with AES-256-GCM, a strong modern cipher, using a key derived from your password with PBKDF2 (120,000 iterations). The locked file contains only random-looking bytes, so no one can read the document without the password. This is genuine file encryption, not just hiding the PDF inside something else.

Know the limits

This is not the same as Adobe's built-in PDF password feature: a locked file cannot be opened directly in Adobe Reader or a browser viewer; you unlock it here with the same password. There is no password recovery, so write the password down. Also note that browser-based encryption, while strong, is weaker than dedicated desktop security tools against a targeted attack on a compromised device.

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PDF Password Protect FAQs

Will the locked PDF open in Adobe Reader?
No. Files locked here use AES file encryption and must be unlocked in this tool with the same password. Adobe Reader cannot open them directly.
What happens if I forget the password?
The file cannot be recovered. AES-256 encryption has no backdoor, so store the password somewhere safe before locking important documents.
How strong is the encryption?
AES-256-GCM with a PBKDF2 key derived over 120,000 iterations. It is strong for everyday protection, though a dedicated desktop tool on a trusted machine offers more hardening.
Does the file get uploaded anywhere?
No. Encryption and decryption run entirely in your browser via the Web Crypto API. Your PDF and password never leave your device.
Can I unlock a file locked on another device?
Yes, as long as you have the password. Open this tool on any device, choose Unlock mode, select the locked file and enter the same password.
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