PDF Password Protect

PDF Password Protect adds encryption to a PDF file so that anyone trying to open it must enter the password you set. It is the digital equivalent of putting a document in a sealed envelope — the content is not visible until the correct key is provided. The tool uses the standard PDF encryption mechanism built into the PDF specification (RC4 or AES, depending on the library version), which is supported by all modern PDF readers including Adobe Acrobat, Preview on Mac, Chrome, Edge, and mobile PDF apps. When someone opens the protected PDF, they are prompted for the password. Without it, the file cannot be opened — the content is encrypted at rest. The encryption is performed entirely in your browser using pdf-lib. The password you type is used only as a local encryption key and is never transmitted or stored anywhere. The original PDF, the password, and the encrypted output all remain on your device. This is critical for security — if the password were sent to a server, the encryption would be meaningless because the server operator could read your document. You should choose a strong password — at least 8 characters, ideally a mix of letters, numbers, and symbols. The tool also sets a separate owner password (your password with _owner appended internally), which in desktop PDF applications allows overriding restrictions like printing or copying. For most users, the user password (the one you type) is what matters — it is the one required to open the file. Important caveats: once a PDF is encrypted, the only way to open it is with the password. If you forget the password, there is no recovery mechanism. The encryption is not a guarantee against a determined attacker with access to PDF cracking tools — it provides a practical barrier for everyday document sharing. For highly sensitive documents, consider additional protections beyond password encryption.