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How to Lock a PDF With a Password, and How to Unlock One

By the Datatool360 team ·

A password is the simplest way to keep a PDF private when you send it by email. It also gets in the way: you type it every time, or you forget it, or another tool refuses to open the file. This guide covers both directions, locking and unlocking, and the limits that are good to know about.

Want to do it right now? Open the Lock & Unlock PDF tool

Lock a PDF step by step

  1. Open the Lock & Unlock PDF tool, choose Lock PDF and add your files.
  2. Type a password, and type it again. The two must match.
  3. If you like, tick printing, copying or editing to ask programs not to allow them (see below for what that really does).
  4. Press Lock PDF. One file is saved as a PDF, several files come as a ZIP.

The new file is encrypted with AES-256, which is the strongest kind of encryption that PDF offers. The work is done in your browser: neither the file nor the password is uploaded.

Choosing a password that is worth something

The encryption is strong, so the password is the weak point. “1234” or a birth date is guessed in seconds by a program. A longer one is far better than a clever short one. Three or four unrelated words (“blue-ladder-monsoon-tea”) are easier to remember than a random jumble and much harder to crack.

Then send the password in another way than the file: not in the same email, for example by a message or a phone call.

And remember it. Nobody can recover a forgotten password for a file locked this way, including us.

The printing and copying options

Tick “printing”, “copying” or “editing” and the file asks PDF programs to refuse those actions, even to someone who knows the password. Most programs follow this, but not all, and some tools ignore it. Treat it as a polite request, not a lock. The only thing that really keeps the file closed is the password.

Unlock a PDF step by step

  1. Choose Unlock PDF at the top of the tool and add your files.
  2. Type the password of the PDF. With several files, the same password is tried on each of them. Files with another password are reported and the others still work.
  3. Press Unlock PDF. You get a copy that opens without asking for a password. Nothing else about the pages is changed.

This tool needs the right password. It does not guess or crack passwords. If the password is wrong, you are told so and nothing is produced.

Two kinds of PDF passwords

  • An open password (also called the user password) is asked for whenever you open the file. This is what the Unlock tool needs.
  • A permissions password (the owner password) lets the file open freely but blocks things such as printing or copying. A file that has only this kind of password can be unlocked without typing anything, and that also removes the restrictions. Please do this only with files that you are allowed to change.

When it does not work

  • The tool says the password is not correct. Check capital letters, spaces and the keyboard language. Letters that look alike (O and 0, l and 1) are the usual suspects.
  • You forgot the password. It cannot be recovered here. Ask whoever made the file for the password or for a new copy.
  • You want to lock a file that already has a password. Unlock it first, then lock the copy with the new password.
  • The file is damaged or is not a PDF. The tool says so, and the other files of the same batch are still processed.

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