Most PDF security advice conflates three completely different mechanisms. Encryption makes a file unreadable without a key, and it holds. Permission flags ask a reader not to allow printing or copying, and a reader is free to ignore them. A watermark is a label that anyone can crop off.
Only the first of those is protection. The tools here are labelled accordingly, and none of them will imply more than it delivers.
Which one do you need?
The file must not be readable without a password
Protect PDF encrypts with AES-256. Without the password the document cannot be opened by any means. Write the password down before you close the page - there is no recovery, here or anywhere.
You have the password and want rid of it
Unlock PDF removes encryption from a file you can already open. The password is mandatory. Nothing here guesses, brute-forces or cracks, and that is a deliberate position rather than a missing feature.
Something in the document must be gone, not covered
Redact PDF deletes the characters you name from the file itself. A black box drawn in an editor leaves the text underneath, one select-and-copy away from anyone who looks.
You only need the document labelled
Add Watermark stamps a status across the pages, and Flatten PDF fixes form entries so they cannot be edited or cleared. Neither is security; both are useful.
At a glance
| Mechanism | Enforced by | Defeatable? | Honest description |
|---|---|---|---|
| AES-256 encryption | Mathematics | No | Actual protection |
| Permission flags | The reader, voluntarily | Yes, trivially | A polite request |
| Watermark | Nothing | Yes - crop it | A visible label |
| Redaction | Deletion of the data | No | The text is gone |
Before you keep the result
- Write the password down before encrypting. There is no recovery of any kind.
- Send an encrypted file and its password by different routes, or you have achieved nothing.
- After redacting, reopen the result and search for the term yourself. This step is not optional.
- Redaction removes page text; your name may still sit in the file's metadata. Check that separately.
Questions and answers
Can you recover or crack a PDF password?
No. Nothing here attempts it. A PDF encrypted with AES-256 and a decent password is not opened by guessing, by us or by anyone else, and a site that offers to crack one is either lying or targeting files that were never properly encrypted.
Is a password-protected PDF genuinely secure?
The encryption is. Everything built around it - a weak password, the password sent in the same email, an unprotected copy left in a downloads folder - usually is not.
Why will you not remove a watermark?
A watermark normally states a document's ownership or licence. Removing one to pass the document on is not something this site is going to help with.