How to Password Protect a PDF Before Sending It

1. 1

   Open Protect PDF

   Drop your file into Protect PDF. The file and the password stay in your browser.

2. 2

   Set the password

   Type a password of at least 4 characters and confirm it. The strength indicator shows whether it is weak, medium or strong; aim for strong.

3. 3

   Download the locked copy

   The new PDF asks for the password before it opens in Acrobat, Preview, Chrome, Edge and every other standard reader.

A PDF can carry two passwords. The user password is the one people need to open the file. The optional owner password controls permissions such as editing. If you set only a user password, it is used for both, which is the right choice for most documents you send to someone.

Drible uses the 128-bit encryption defined in the PDF standard, which every PDF reader can open. It keeps the contents unreadable to anyone without the password, and in practice the password itself is the weak point: short or common passwords can be guessed by software that tries millions of combinations.

Use a passphrase of four or more random words, or 12 or more mixed characters. For highly sensitive material, such as legal evidence or medical records sent outside your organization, prefer software that offers AES-256 encryption together with a long passphrase, or a secure file-sharing service with access controls.

A locked PDF is only as safe as the way its password travels:

• Never put the password in the same email as the file. Anyone who sees one sees both.
• Send it by a different channel: a text message, a phone call or a messaging app.
• Agree on a pattern in advance for regular exchanges, for example a reference number the recipient already knows.
• Keep a copy of the password yourself. It cannot be recovered if it is lost, because it is not stored anywhere.

Do everything else first. A locked PDF is harder to edit, so finish signing, merging and compressing before adding the password. If the file is too large to email, run it through Compress PDF and then protect the result; the email size guide explains the settings. When you receive a locked PDF and need an open copy for yourself, Unlock PDF removes the password, provided you know it; see how to remove a password from a PDF.