PDF Password: Protect or Unlock

About the PDF Password

This tool does two jobs. Protect PDF encrypts a PDF so that it asks for a password before it opens. It uses the standard PDF password method with 128-bit AES (security handler revision 4, introduced with PDF 1.6), which current PDF readers support, including Adobe Acrobat Reader and the viewers built into Chrome, Edge, Firefox and Safari. Every string and data stream in the file is encrypted with a key derived from your password, so the text, images and document details such as the title cannot be read without it. The basic structure of the file, such as its number of pages, is not hidden.

Be clear about what this protects. The password controls opening the file. Once someone has opened it with the password, they can read, print, copy and edit it as normal: the tool does not set printing or copying restrictions, because such restrictions are only advisory flags that not every PDF program honours. Choose a password of 4 to 32 characters using English letters, digits and standard symbols (PDF password protection of this type only uses the first 32 characters, and readers handle accented letters inconsistently). This tool cannot recover a forgotten password, so store it safely.

Unlock PDF removes encryption from a PDF when you know its password and saves an ordinary, unprotected copy. It reads the common password-based methods: 40-bit and 128-bit RC4, 128-bit AES and 256-bit AES. It does not guess or crack passwords. For example, a bank statement arrives protected with your date of birth; unlock it once with that password so you can merge it with other statements or compress it for an upload form. If a PDF opens without a password but restricts printing or copying, leaving the password field empty produces an unrestricted copy; only do that with files you are entitled to change.