Password Protect a PDF
Lock a PDF with a password so it cannot be opened without one. The document is encrypted with AES 256 here in your browser, so the password and the file both stay on your machine. Nothing is uploaded, and nobody else ever sees either.
- Nothing uploaded
- Works with no signal
- No sign up
- Quality unchanged
Nothing loaded yet.
The pages
Load a PDF to see its pages.
Once built, the file cannot be opened without the password. There is no way to recover it, not by us and not by anyone else.
Your PDF and your password never leave this device.The file is opened by your browser, the encryption happens here in the page, and the download comes from your own machine. The password is never transmitted, never stored, and never seen by anyone but you.
A password you cannot recover
Because the encryption happens on your machine and the password is never sent anywhere, there is no copy of it for anyone to look up. Lose it and the document is gone. That is what makes it worth using, and it is also the thing to be careful about before you press the button.
How to use this tool
Drop a PDF on the box at the top, then type a password twice. The second box exists so a typo cannot lock you out of your own document, which is a mistake with no way back.
Press the button and the encrypted file downloads from your own machine. Nothing about the process touches a server.
Why doing this in the browser matters here
Every tool on this site runs locally, but for this one it is the whole point rather than a convenience.
Uploading a document to be password protected means handing both the document and the password to somebody else, and trusting them with the one thing the password was supposed to protect. Even an honest service has your file on a disk somewhere for a while.
Here the encryption happens in the tab. Open the network panel in your browser tools and lock something: there is no upload request to see, because there is no upload.
What AES 256 does and does not mean
The document is encrypted with AES 256, written as revision 5 of the standard security handler. Worth knowing what that is and is not, because the phrase gets used loosely.
It is genuinely strong compared with the alternative. Some tools still produce RC4 at forty or a hundred and twenty eight bits, which is decades old and should not be used for anything that matters. A file encrypted here cannot be opened by reading it in a text editor, and its content is not sitting in the file waiting to be found.
Revision 5 is Adobe original AES 256 rather than the later revision 6 defined in ISO 32000-2. The difference is in how the password becomes a key: revision 5 uses a single pass of SHA 256, while revision 6 repeats the hashing many times to make guessing slower. So a short or common password is easier to attack here than it would be under revision 6.
The practical answer to that is length. A long password matters far more than a clever one, and it is the one thing entirely in your control.
Permissions are not a lock
The printing, copying and editing settings are recorded in the document and every well behaved reader respects them. Software that ignores them also exists, and it is not hard to find.
Treat those settings as a clear statement of what you intended, useful for an honest reader and worth setting. The password is the part that actually stops someone.
A worked check you can repeat
Lock a document, then try to open the result in any PDF reader. It asks for a password. Give it the wrong one and it refuses. Give it the right one and the document opens normally.
Open the encrypted file in a text editor and search for a phrase you know is in the document. It is not there, because the page content is encrypted rather than merely marked as restricted.
That check was run before publishing, in two different places. The encrypted output was opened with an independent PDF reader with no password, with a wrong password, with the user password and with the owner password. The first two were refused, the second two opened and the text came back intact. The same four checks were then repeated against the copy running here in the browser.
Mistakes that catch people out
Not writing the password down first. There is no recovery. None, by anybody.
Choosing something short. Length beats complexity. A long phrase you can remember is better than eight characters of punctuation.
Sending the password the same way as the file. A locked document attached to an email that contains the password is not locked in any useful sense.
Relying on the permissions. They ask politely. They do not enforce.
Trying to protect an already protected file. It cannot be opened here in the first place. Remove the existing password first, in software that has it.
Common questions
Is my PDF or my password uploaded anywhere?
No. Both stay in this browser tab. The encryption happens on your machine and the download comes from it, so the password is never transmitted and never stored.
What encryption is used?
AES 256, written as revision 5 of the PDF standard security handler. That is far stronger than the RC4 that some tools still quietly use.
Can you recover my password if I forget it?
No, and neither can anyone else. No copy of it exists outside your own tab. That is the point of doing it this way, and the reason to write it down somewhere safe first.
What is the owner password for?
It controls the permissions rather than opening the file. Leave it blank and the same password does both jobs.
Do the permissions actually stop anyone?
Not really. Permissions are a request to the reader software, and software that ignores them exists. The password is the real lock; the permissions are a statement of intent.
Can I remove the password later?
Not with this tool. It adds protection rather than taking it away, and a PDF that is already encrypted cannot be opened here.
Related PDF tools and reference
Reference: ISO 32000, the standard that defines the PDF security handler used here.