How to password-protect a PDF

Email is not a locked box. Attachments sit in inboxes for years, get forwarded, and get synced to phones that get lost. If you are sending a tax return, a medical report or a list of account numbers, a password on the PDF adds a lock that travels with the file.

Lock it in three steps

1. Open Protect PDF and drop in the document. It stays on your device the whole time.
2. Type a password twice, and decide whether people who open it may print, copy or edit it.
3. Download the protected file. Anyone opening it is asked for the password.

The file is encrypted with AES-256, the strongest the PDF format supports. AES-128 is offered for very old PDF readers that can't open AES-256.

Share the password separately

A password sent in the same email as the file protects nothing. Text it, say it on the phone, or agree on one in advance. Use something long: a short phrase of four or five unrelated words is both strong and easy to read out.

Keep a copy of the password

The password isn't stored anywhere, including in the file, so if you forget it, the document can't be opened. Keep the unprotected original somewhere safe, or store the password in a password manager.

Removing a password

Tired of typing a password on your own documents? Unlock PDF saves a copy that opens without one. You need to know the password: it removes a password you already have, and doesn't guess or crack them.