How to password protect a PDF on a Mac

With PDF Unlimited (free)

1. Open the PDF

   Open the file you want to protect in PDF Unlimited.

2. Choose Password Protect

   Choose File > Password Protect…

3. Set the password

   Type a password and confirm it. Use something long that you do not use anywhere else.

4. Save a protected copy

   Save the protected version. Keep an unprotected original somewhere safe on your Mac if you will need to edit it later.

5. Test it

   Close the file and open it again. It should ask for the password before showing anything.

With Preview, built into macOS

1. Export a copy

   Open the PDF in Preview and choose File > Export. Give the copy a new name to keep the original unprotected.

2. Open Permissions

   Click Permissions. Select Require Password To Open Document and enter the password twice.

3. Set the owner password

   Choose which actions, like printing or making changes, are allowed without the owner password, then enter an owner password. It can be the same or different.

4. Apply and save

   Click Apply, then Save. To change it later, open the PDF and choose File > Edit Permissions.

Open passwords versus permissions

An open password stops anyone from viewing the file without it. That is what most people want when emailing tax documents or contracts.

A permissions or owner password lets people open the file but asks some apps to block printing, copying or editing. Treat permissions as a polite request. Plenty of software ignores them. If the content is truly private, use an open password.

Share the password the smart way

A password in the same email as the attachment protects nothing. Send the file by email and the password by text message, a phone call, or a password manager's sharing feature.

Pick something long rather than clever. Four random words are easier to read out over the phone and harder to guess than a short string of symbols.

Do not lose it

There is no "forgot password" link on a PDF. If you lose the open password, the file is effectively gone. Keep the unprotected original on your Mac, or save the password in your password manager.

Other ways to protect a PDF

A password controls who can open the file. It does not control what they do once it is open. If the recipient should never see certain details at all, redact them before you send. And if the file is too big to email after you protect it, compress it first, then add the password.

When to use a password

Not every PDF needs one. A menu or a flyer does not. A good rule: if you would not want the file forwarded to a stranger, lock it. That covers tax forms, payslips, bank statements, medical records, signed contracts and anything with an ID number, date of birth or account number.

Passwords add a small hassle for the person receiving the file, so tell them it is coming and how they will get the password.

Questions