May 9, 2026 · Protect PDF
How To Password-Protect A PDF
Emailing an unprotected contract is the digital equivalent of handing it to a stranger in the elevator. Anyone who intercepts the message - intentionally or not - can read it.
Protect PDF adds an AES-256 password to a PDF in one step. Without the password, the file is unreadable. With it, the file works in every major PDF reader.
AES-256 Encryption
AES-256 is the standard symmetric cipher used by governments and banks. A modern attacker without the password cannot read the file - the math doesn't allow it within any reasonable time frame.
Practically, this means the security of your PDF reduces to the security of your password. Use a long, hard-to-guess password. "Password123" defeats the encryption; a long passphrase doesn't.
How To Protect
Open Protect PDF. Drop in your PDF. Set a password. Confirm it (to catch typos - we can't recover a mistyped password). Click Protect. Download the encrypted file.
Share the password through a different channel than the file itself. If both travel together over the same email, an interceptor gets both.
We Don't Keep Your Password
The password is sent over HTTPS to the worker, used once to encrypt the file, and never written to logs or storage. We can't recover it for you if you lose it - that's a feature, not a bug.
The encrypted PDF is deleted within 24 hours. After that, even we have nothing to give you.
When To Use vs Other Tools
Use Protect PDF when you need cryptographic confidentiality. Use Watermark PDF when you need to communicate intent (DRAFT, CONFIDENTIAL) without preventing reading. Use Flatten PDF to prevent form-value editing.
These compose. Watermark first, then flatten, then protect - and the file is locked down at every level.
Lock down a sensitive PDF with Protect PDF. AES-256 encryption, no password storage, files deleted within 24 hours.