What password-locking a PDF actually protects
Adding a password to a PDF encrypts the document itself, so anyone who intercepts the file in transit — over email, a shared drive, or a messaging app — can't open it without the password, which you'd share through a separate channel. It's a meaningfully different protection than just relying on the platform you're sending it through to be secure.
PrivaPDF applies standard PDF encryption compatible with Adobe Acrobat and other major readers, and because the password is only ever used inside your browser's local WebAssembly runtime, it's never transmitted anywhere — including to PrivaPDF itself.