PDF 密碼保護工具

This PDF protector adds a password to a document with AES-256 encryption, so only people who know the password can open it. The text and quality are preserved exactly.

Password-protecting a PDF is the right move before sending anything sensitive by email or a shared link, a contract, a bank statement, a payslip, an ID, where you do not want anyone who gets the file to be able to read it.

It runs entirely in your browser using QPDF compiled to WebAssembly, so your PDF and the password never leave your device.

Protecting is lossless: it does not rebuild or rasterize the document, so all text, images and fonts stay exactly as they were and the file remains searchable once unlocked.

The encryption is real, not a flimsy restriction. AES-256 is the strongest standard PDF encryption, so without the password the contents cannot be read, even by someone who has the file.

The result is a standard encrypted PDF, so it opens in any modern reader, Acrobat, Preview, browsers and phones, after prompting for the password. There is nothing proprietary about it.

Only the password protects the file, so keep it safe: without it, an AES-256 encrypted PDF cannot be read. The companion PDF unlock tool removes a password when you know it.