Add a password to a sensitive PDF, or remove one you already know. It uses strong 256-bit AES encryption and runs in your browser — your file is never uploaded.
Switch the action to “Remove a password”, enter the PDF's current password, and download an unlocked copy. This only works when you know the password.
This is deliberate. A tool that bypassed encryption would put everyone's protected documents at risk. meldpdf only helps you protect your own files, or unlock ones you already have the password for.
256-bit AES is only as strong as the password behind it. Use a long, unique passphrase, and share it with the recipient through a separate channel (not in the same email as the PDF).
No — encryption runs in your browser. The engine downloads once; your file never leaves your device. See our privacy policy.
No. That would be cracking encryption, which we don't do. You need the current password.
256-bit AES, the strongest standard PDF encryption.
When you add a password with this tool, the PDF is encrypted using AES-256 (Advanced Encryption Standard with a 256-bit key). This is the strongest encryption level defined in the PDF specification and the same standard used by governments and financial institutions to protect classified data. The encryption scrambles the file's contents so that without the correct password, the data is unreadable — not just hidden, but mathematically inaccessible.
The PDF format actually supports two types of password: a user password (sometimes called the "open password") that prevents anyone from opening the file, and an owner password (sometimes called the "permissions password") that restricts actions like printing, copying text, or editing while still allowing the file to be opened. This tool sets a user password — the stronger of the two — which means the file cannot be opened at all without the correct password.
Password protection is worth using whenever a PDF contains information you would not want a stranger to read. Common situations include:
Always share the password through a different channel than the PDF itself. Putting both in the same email defeats the purpose.
PDF encryption is strong, but it is worth understanding its boundaries:
The file is permanently locked. There is no backdoor, no recovery option, and no way for meldpdf or anyone else to open it. This is by design — if the password could be recovered, the encryption would be meaningless. Always store your password in a password manager or other secure place.
Yes. This tool runs in any modern browser, including on iOS and Android. The encryption engine downloads once and works the same way as on a desktop computer.
Last updated: 3 September 2026.