Set a password so a PDF can't be opened without it. The file and the password you choose are processed locally and never transmitted anywhere — for a document you're locking down specifically because it's sensitive, that matters more than most.
Upload a PDF, choose a password, and download a copy that requires it to open.
There's no way to recover it — since the password is never sent anywhere or stored by this site, nobody but you ever has it. Write it down somewhere safe before closing this tab.
Not with this tool — this only adds protection to an unprotected PDF. You'll need the original, unprotected file to start from.
It uses standard PDF encryption that any PDF reader can open with the correct password, the same underlying approach desktop PDF tools use — just running locally in your browser instead of installed software.