Password-protect a PDF. AES-256, without uploading it
Before emailing a contract, a medical result, or a tax document, it is worth locking it so only the intended recipient can open it. This tool encrypts your PDF with a password using qpdf compiled to WebAssembly, applying AES-256. The same strong, modern encryption standard used for serious document security. The irony of most online “protect PDF” tools is that you upload an unprotected copy of your sensitive file to a stranger’s server to secure it. Here that never happens: the encryption runs in your browser, so the document is protected on your own machine and only the finished, encrypted file exists to be shared. Choose a strong password and share it with the recipient through a separate channel.
How it works
- Drop the PDF you want to protect below.
- Choose a password. Anyone opening the file will need it.
- Download the encrypted PDF and share the password separately from the file.
Frequently asked questions
How strong is the encryption?
It uses AES-256, the current standard for strong PDF encryption, applied by qpdf. The real-world security then depends on your password: a long, unique passphrase is far harder to attack than a short, guessable one.
Will the protected PDF open everywhere?
Yes. AES-256 PDF encryption is supported by Acrobat, macOS Preview, current browsers, and mainstream mobile PDF apps. The recipient simply enters the password when they open the file.
Is my document uploaded to encrypt it?
No. Uploading an unprotected copy in order to secure it would create an unnecessary risk. qpdf encrypts the document locally in your browser.
What if I forget the password?
There is no recovery. That is what strong encryption means. Store the password somewhere safe (a password manager is ideal). If you need to remove it later from a copy, the Unlock PDF tool does that when you supply the password.