PDF Password
Lock a PDF with a password, change it, or remove one you know.
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What the lock does
Your password encrypts the whole file with AES-256. Without it the contents are unreadable, not just hidden.
What it needs first
The first time, your browser downloads the lock engine (about 2 MB) and keeps it. After that the tool works the same, and nothing about your file is ever sent.
What it runs on
The lock engine is pdfstudio, which packages qpdf as WebAssembly. We're working on our own PDF library so this leans less on third-party code.
Questions
Does the password get sent anywhere?
No. The password and the file stay in your browser, which is the point. Most sites like this upload both to a server.
How strong is the lock?
AES-256, the strongest scheme PDF supports. Strength still depends on your password, so a long one beats a clever short one.
Can you unlock a PDF I forgot the password to?
No. Unlock only works with the correct password, and nothing here guesses or cracks one. A forgotten password can't be recovered.
Can I change a PDF password?
Yes. Drop a locked PDF, pick "Change the password", enter the current one and a new one. The result is re-encrypted with AES-256, even if the old file used something weaker.
Will the locked PDF open everywhere?
In current viewers, yes: Acrobat, Preview, and the major browsers. Very old readers may not handle AES-256.
Does this upload my files anywhere?
No. Everything runs in your browser. Files never leave your device, there's no server to send them to, and no account or log.