How to Password Protect a PDF File

Desktop-side

• macOS Preview: File → Export → Encrypt
• Windows PDF encryption tool: requires additional purchase
• Adobe Acrobat: Edit → Protect

In-browser password addition

We don’t currently offer a browser-side PDF password tool (pdf-lib supports AES encryption but requires correct IV handling). Common out-of-browser approaches:

1. qpdf command line: qpdf --encrypt user_pw owner_pw 256 – input.pdf output.pdf
2. macOS Preview
3. Adobe Acrobat

Note

A password only protects the file at viewing time. It doesn’t prevent someone who has already received the file from copying the content. For real protection of sensitive documents, use a PDF encryption + rights-controlled DRM solution.