Password-Protecting a PDF With Real AES Encryption

Jul 26, 2026 · 4 min read · Security

Password-Protecting a PDF With Real AES Encryption

Password-protecting a document on a website is usually a contradiction: you upload the file and the password to someone else’s server and trust them with both. Here the encryption happens in your browser - the password never exists anywhere but your machine.

How to use it

  1. Open Protect PDF and choose the document.
  2. Set the open password (and optionally a separate owner password with print/copy permissions).
  3. Process and download - the file now demands the password in any reader.

Try it now: open the Protect PDF tool - no account, no upload, free.

What happens under the hood

The document is encrypted with AES-256, the standard modern PDF readers implement, using keys derived from your password - all computed locally. Permissions (printing, copying) are enforced by cooperating readers; the open password is enforced by mathematics.

Tips for better results

  • The open password is the real protection. Permission flags without one are honored by polite software only.
  • Use the Password Generator tool for the password, and share it over a different channel than the file.

Privacy, in one sentence

Your file is read into your browser's memory, processed there by JavaScript and WebAssembly, and handed back to you as a download - no server ever sees a byte of it. Close the tab and nothing remains.

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