Protect PDF
Add password protection (AES-256) to a PDF, right in your browser.
About this tool
Adds password protection to a PDF, encrypting it with AES-256 (the current standard, supported by all modern PDF readers) so it can only be opened with the password you set. You can also restrict what someone can do once it's open — printing, copying text, or editing — independent of the password itself.
Encryption happens entirely in your browser using the open-source pdf-lib library and your browser's built-in Web Crypto API; your file and password are never uploaded anywhere.
Frequently asked questions
- What happens if I forget the password?
- The PDF becomes permanently unreadable — AES-256 encryption has no back door or recovery option, by design. Store the password somewhere safe before closing this tab.
- Can the permission restrictions (no printing/copying/editing) actually stop someone?
- They're enforced by compliant PDF readers, but like all PDF permission flags, they're not a hard technical guarantee — determined users with certain tools can bypass them. Only the open password itself (requiring AES-256 decryption) is cryptographically strong protection.
- Is my PDF or password uploaded anywhere?
- No — encryption happens entirely on your device using your browser's own cryptography APIs. Nothing is sent to any server.
- Will this work with an already-encrypted PDF?
- No — this tool expects a normal, unprotected PDF as input. To change the password on an already-protected file, use the Unlock PDF tool first, then protect it again with the new password.