PDF toolsA PDF can carry two different kinds of password, and they protect different things. An open password (sometimes called a user password) encrypts the whole document: without it, the file won't open in any reader at all. A permissions password (an owner password) leaves the file readable but restricts actions like printing, copying text or editing, for readers who follow the rules enforced by their PDF software. Protect PDF sets the open password: the one that actually stops someone from reading the file.
How the encryption works
Modern PDF encryption (AES-256, the current standard) scrambles the file's contents so that without the correct password, the data is unreadable, not just hidden. This happens entirely in your browser: the file and the password you choose never leave your device, so there's no server in between that could keep a copy of either.
What a password doesn't protect against
It's worth being precise about the limits. Once someone has the password and the file is open, nothing stops them from taking a screenshot, printing it, or retyping what they read. A password protects the file in transit and at rest, such as sitting in an inbox or a shared drive, not what a legitimate reader chooses to do with the content afterwards. It also isn't a substitute for a digital signature if what you need is proof of who approved a document; that's a separate feature, covered in electronic vs digital signatures.
Choosing and sharing the password
Use a password the recipient can actually receive and type, not just a strong one. A short passphrase sent through a different channel than the email carrying the PDF, a text message or a phone call, is both more secure and more usable than a complex password typed into the same email thread as the attachment, which defeats the purpose if that inbox is ever compromised.
If you forget it
There's no recovery option, by design: a password a company could quietly bypass wouldn't be protecting much. If you encrypted your own file and lost the password, Unlock PDF can remove protection from a file if you already know the password (useful once a document no longer needs to be locked), but it cannot recover a password you don't have.
Questions
What encryption does this use?
AES-256, the current PDF encryption standard, applied entirely in your browser.
Can I remove a password later?
Yes, with Unlock PDF, as long as you still know the current password. There's no way to remove a password you don't know; that's what makes it meaningful protection.
Does a password stop someone from printing or copying the text?
Not once the file is open with the correct password. If you need to restrict printing or copying for readers who already have access, that's a separate permissions setting handled differently than the open password described here.
Is my file uploaded to set the password?
No. The file is read and encrypted inside your browser and never sent to a server.