Password-protect a PDF without sending it to a server
Encrypt a PDF with a password in the browser, or remove a protection you own — without transmitting the document or the password.
Published on 5 min readby Hamza El Hajjaji
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Table of contents
Why encrypt a PDF
A PDF travels: attachment, USB stick, shared folder. A password turns the file into a safe — readable only by whoever holds the key. Useful for contracts, statements and files that need to move.
Protecting a document by sending it to a third-party server means handing over the content before locking it — and transmitting your chosen password along the way. Local protection happens entirely in the browser: the file only leaves in encrypted form, and the password never leaves your machine.
Unlocking a PDF
The reverse operation exists too: for a document whose password you own, the unlock tool produces an unprotected copy — handy before archiving or processing with tools that refuse encrypted files.
Best practices
Long passphrase rather than a short complex password.
Separate channel: send the password through a different medium than the file.
Keep the original: the encrypted file and the clear original are two distinct files.
No store, no account: a two-click install, double-click to open a PDF, Android share target, and a full offline mode once you have visited the site online once.
Summarizing, translating and searching a PDF with models running inside the browser: what Chrome's built-in AI APIs and Transformers.js change for document privacy.
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