How strong is the protection?
The file is encrypted with AES-256, the strongest encryption in the PDF standard (PDF 2.0 / Acrobat X and later). Without the password the content can't be read; with a good password it can't practically be guessed. The weak point is almost always the password itself, so use at least 12 characters, or four random words. The strength indicator gives a rough idea.
Encryption is done by qpdf, a widely used open-source PDF library, compiled to WebAssembly so it runs in your browser. Your password is never sent anywhere — which also means we can't recover it for you. Keep it somewhere safe.
Opening password vs. restrictions
The password to open is required to view the file at all. Restrictions (no printing, no copying, no editing) are different: they're enforced by the PDF app rather than by encryption of the content, and are protected by a separate permissions password. If you leave that empty, a random one is generated so the restrictions can't be lifted with the open password.
Compatibility
AES-256 PDFs open in Adobe Acrobat and Reader, macOS Preview, Chrome, Edge, Firefox and current mobile apps. Very old software (before 2010) may not open them. To remove the password later, use Remove PDF password.
Are my files uploaded?
No. Encryption runs with JavaScript and WebAssembly running in your browser tab. Your files are read from your device and the results are created on your device; nothing is sent to gratistools.be or anyone else, which is also why there are no queues, daily limits or watermarks. See the privacy page.