Unlock PDF

How the Unlock PDF works

Bank statements, payslips, tax forms and scanned contracts often arrive locked. The password is usually your date of birth, a policy number or part of your postcode, and every time you open the file you have to dig it out again. Other tools in a workflow, such as mergers, compressors and form fillers, refuse to work on an encrypted file at all. Removing the protection once, from a copy you keep somewhere safe, solves both problems.

How to unlock PDF files

1. Drop the locked PDF into the box.
2. Type the password. If the file opens without one but will not let you print or copy, leave the box empty.
3. Run the tool and download the copy ending in -unlocked.pdf.

The stats show which kind of encryption was removed and whether the open password or the owner password was used.

Two kinds of PDF password

A PDF can carry two passwords, and they do different jobs.

A file with only an owner password opens in any reader, but the reader is asked to block some actions. That request is all it is: the content is encrypted with a key anyone can derive, so the restrictions are removed without a password. A file with an open password is different. Its key comes from the password, and without the right one the content cannot be read by anyone.

Either password unlocks the file here. The owner password is accepted wherever the open password is, because it can also recover the encryption key.

Encryption it handles

These are the methods of the standard PDF security handler, which covers nearly every locked PDF. Files protected with a digital certificate or a vendor's own rights management plug-in use a different handler and are refused with a message that says so.

How it works

The tool reads the encryption settings from the file and checks your password the way the PDF standard describes: MD5 and RC4 for the older methods, and the SHA-2 based hash with at least 64 hundred AES rounds for 256-bit files. A match gives the file's encryption key. Every string and every stream in the document, including those packed inside object streams, is then decrypted with the key for its object, and the file is saved again without its encryption dictionary.

Decryption uses your browser's built-in Web Crypto for AES, so it is fast even on large files. Page content, fonts and images come out byte for byte as they were before encryption, so nothing is re-compressed or redrawn.

Tips and pitfalls

Passwords are case sensitive. Banks often use a mix such as the first four letters of your name in capitals plus your birth year. Check the email or letter that came with the file for the format.

Wrong password or no password? If the tool says the file needs a password, it has an open password and the empty box was not enough. If it says the password is wrong, the file was found and read, but neither of its passwords matched what you typed.

Keep the unlocked copy private. The new file has no protection at all. Store it where you keep other personal documents, and do not email it if the original was locked for a reason.

Only unlock files you are entitled to. Removing a password you were given, or restrictions on your own documents, is routine. Breaking protection on someone else's file is not something this tool helps with: without the open password the content stays encrypted.

Damaged and locked? Unlock first, then run the unlocked copy through Repair PDF. The repair tool cannot read encrypted content.

Reading the result

Encryption removed names the method that was on the file. Password used says "Open password", "Owner password", or "None needed" when the file only carried restrictions. If no password was needed, a note confirms that the print, copy and edit restrictions were lifted.

Related tools