How to Password Protect a PDF on Mac (Free)

A contract, a bank statement, or a private report needs to stay readable only by the person you send it to. Locking the PDF with a password is the simplest way to make sure of that. On a Mac, you have two good free options: the built-in Preview app, and a browser-based protect tool for more control.

Here is how to password protect a PDF on a Mac for free.

Protect a PDF with Preview (built in)

1. 1Open the PDF in Preview on your Mac.
2. 2Choose File > Export.
3. 3Tick the Encrypt checkbox near the bottom of the export window.
4. 4Enter a strong password and verify it.
5. 5Click Export — the saved copy is now password-protected.

Preview’s built-in encryption is free and needs no extra software. The exported file requires the password every time it is opened.

Protect a PDF in your browser (more controls)

Preview is quick, but a browser-based protect tool gives you additional options, such as processing a file that will not open in Preview or keeping everything locally with clear feedback:

1. 1Open the Protect PDF tool in Safari or Chrome on your Mac.
2. 2Drag the PDF into the tool, or click to browse for it.
3. 3Enter a strong password — at least 12 characters, ideally a short phrase.
4. 4Confirm the password and click protect.
5. 5Download the encrypted PDF back to your Mac.

The tool runs in your browser tab, so the document is processed on your Mac and not uploaded anywhere.

What password protection actually does

• It encrypts the document with AES so a password is needed to open it
• It stops casual access — a stolen file without the password is useless
• It is not the same as editing restrictions, which only limit changes

Modern encryption has no backdoor, so forgetting the password means losing access to the file. Store it in a password manager, or keep an unprotected backup copy somewhere safe.

Choosing a password that survives

Sharing the protected PDF

Send the file one way and the password another — an encrypted file delivered in the same email as its password is not protected. Send the PDF by email and share the password by text, call, or a messaging app. If the document is urgent, call the recipient and read the password aloud.

Preview and a browser tool both encrypt your PDF on a Mac without costing anything. Pick Preview for a quick lock, or a browser tool when you want a simple step-by-step flow for multiple files.