Unlock PDF

About Unlock PDF

This tool removes standard security handler encryption from a PDF and gives you a copy without a password or permission restrictions. When you load a file it first reads the /Encrypt dictionary, shows the method (40- or 128-bit RC4, AES-128, AES-256) and the current permissions, and tests whether an empty password opens it. If an open password is required, it derives the file key from the password you enter, decrypts every string and stream, and writes the file out again.

It is not a password cracker. A file with an open password can only be decrypted if you know either the open password or the owner password; there is no brute-force feature. The intended use is your own files, statements that were sent to you with a known password, and copies made by someone who has the right to make them.

Files that open without a password, and files that do not

Encrypted PDFs fall into two groups. If there is an open (user) password, the content can only be decrypted with a key derived from that password. If the open password is empty and only permissions such as no printing or no copying are set, the file is built so that a key comes out of the empty password, because viewers must be able to open it for anyone. When this tool says a file can be unlocked without a password, you are looking at the second group.

In that case, the only thing standing behind the restrictions is viewer cooperation. The file is technically encrypted, but deriving the key needs no secret. If the author really wanted to stop copying, PDF permissions were never the right mechanism.

When it is fine to unlock a file, and when it is not

Weak as they are, permission restrictions still express what the author wanted. The fact that something can be removed does not mean you are allowed to remove it. The tool was built with situations like these in mind:

• You protected your own document and are tired of typing the password every time.
• A bank, utility, payroll provider or government office sent you your own statement with a password (often your date of birth or part of an ID number), and the system you need to upload it to rejects encrypted PDFs.
• You administer company documents and know the password a former colleague set.
• A screen reader cannot read a file because copying is blocked. Check first: compliant viewers honour the separate accessibility-extraction permission, which is often still allowed.

What is out of scope

Paid e-books, commercial research reports and similar files restricted by a rights holder to prevent copying are not what this tool is for, and neither are files whose password you do not know. In a number of jurisdictions, circumventing a copy-protection measure can be a legal issue in its own right, separate from what you do with the content afterwards. If you are unsure whether you are entitled to an unrestricted copy, ask the sender for one.

The tool also cannot remove protection that is not the standard security handler. Certificate-based encryption (Adobe.PubSec and similar, where the file key is wrapped with each recipient's public key) needs the matching private key, and proprietary DRM such as Adobe LiveCycle or FileOpen fetches keys from a server outside the file. Those files are reported as unsupported.

Decrypting a PDF that contains a digital signature rewrites the file, so signature validation fails afterwards. If the signature's evidential value matters, keep the encrypted original as well. When the original carries a signature, the result screen warns about this again.

Either password works

The specification lets the owner password recover the file key too. In the RC4 and AES-128 schemes, the owner password decrypts the /O value to reveal the user password, which then yields the key. In AES-256 (R6) the /OE entry holds the file key wrapped with the owner password. So whichever password you know is enough, and the result tells you which one authenticated.

Worked examples

How to use it

1. Choose the PDF; the encryption method and permissions are shown first.
2. If an open password is required, enter the open password or the owner password.
3. Run the tool and download the unlocked copy; keep the original if you may need it.

Frequently asked questions