I forgot my PDF password

Is there really no way to open a PDF without the password?

No, not when it is the open password. This is not about lacking the right tool or the money to buy it: the file content is encrypted and the key that decrypts it derives from the password. Until that password is reconstructed, the bytes of the document are noise.

That is correct behaviour, not a defect. A cipher that opened without the key would be no cipher at all, and the same mechanism keeping you out today is what stops someone else reading the document if the file turns up in a forwarded email or on a lost memory stick.

There is one exception that saves a lot of people, which is why the test in the next section is worth doing before giving up: not every PDF password encrypts anything.

How do I tell which of the two passwords my file has?

The PDF format defines two, with similar names and opposite effects. Open the file in the reader you already have and watch what happens.

If the document appears on screen and you can read the text, the content was never encrypted. What exists is a restriction flag that relies on the PDF reader's goodwill to be honoured, and any tool that chooses to ignore it reads and edits the file freely. In that case your problem is solvable, and solvable quickly.

If the reader puts up a password box before showing anything at all, it is the open password. From here on this page deals with that case, which is the hard one.

What can I actually do to get back in?

Ordered by what solves the most real cases, not by what sounds most technical.

1. Ask the sender for the file again. This is the path that works in almost every real case, which is why it is first. A bank, an insurer, an accountant or a payroll department will reissue the document without fuss.
2. Reread the email that carried the file. Institutional documents almost never use an arbitrary password: they use a piece of your own data, and the rule is usually written in the body of the email or on the sender's help page. The common patterns are a tax number, a date of birth in eight digits, a customer number, or the last digits of an account.
3. Search your password manager and your browser's saved passwords. Search for the name of whoever issued the document, not for the file name.
4. Look for the unencrypted original. If you were the one who protected the file, an earlier version often survives: in the folder where you created it, in your backup, or in your sent mail.
5. A local attack, only if you remember the shape of the password. There are programs that run on your own computer and test candidates, such as John the Ripper with the pdf2john utility. It makes sense if you remember it was a four digit PIN or a date. It makes no sense at all against a passphrase you cannot reconstruct.

How much of a chance an attack has, in numbers

Feasibility depends on one thing only: how many candidates exist. Every character added multiplies the search space by the number of possible symbols, and that grows fast.

We do not publish attack speeds, because they depend on the hardware and on the cipher revision and would go stale with nobody noticing. The structural conclusion is enough: if the password was short and predictable, a local attack is realistic; if it was a passphrase, it is not.

Do the services that promise to unlock a PDF work?

They work on the permissions password, which was protecting nothing. For the open password a service has only two possible routes, and neither of them is magic.

• You already know the password and the service merely opens the file with it and saves an unencrypted copy. Legitimate, and you can do exactly the same yourself in your PDF reader.
• You do not know the password and the service tries candidates. That is the same attack described above, with the same odds, run on somebody else's computer.

Be suspicious of any instant result: instant means it was a permissions password. And there is a cost rarely said out loud: to try anything at all, the service needs your file. If the document is a tax return, a medical report or a contract, uploading it hands the content to a third party you do not know, for an attempt that will probably fail.

Why does BestPDFInTheWorld not help here?

For three reasons, and all three are worth stating.

The first is that we have no password removal tool, neither for open nor for permissions passwords. There are thirty-three tools, and the two that touch passwords are protect (which adds one, with AES-128 encryption) and unlock (which removes one, but only with the right password). None of them breaks one.

The second is that the file never reaches us. All processing happens in your browser, there is no server receiving documents, and so we have neither the file nor the password to try anything with. It is the same property that stops us reading your documents, and you cannot have one without the other.

The third, worth stating before you find it yourself: our tools do not open an encrypted PDF, not even when you know the password. There is no field to type it into. The eight tools built on pdf-lib refuse the file with the message "Input document to PDFDocument.load is encrypted", in English, because it comes straight from the library. The ones built on pdf.js (compress, PDF to Word, PDF to image) fail with a password exception.

If you know the password and want to use our tools, decrypt first: open the PDF in your reader with the password, save an unprotected copy (in Acrobat that is File, Properties, Security, no security) and work on that copy.

How do I stop this happening again?

• Store the password in a password manager at the moment you set it, not afterwards. It is the one step that solves the problem completely.
• Keep the unencrypted original too, somewhere only you can reach. An encrypted PDF is a copy, not a vault.
• Do not send the password in the same email as the file. If the email is intercepted, both are, and the encryption bought you nothing.
• Prefer a phrase of four or five unrelated words to a short word with symbols. It is easier to remember and far more expensive to attack.

Sources

• ISO 32000-2, Portable Document Format
• Adobe, proteger PDF com palavras-passe
• Openwall, John the Ripper
• pdf-lib, PDFDocument.load