How to password protect a PDF on a Mac

How to password protect a PDF on a Mac with Deckle

1. Open Password protect PDF in Safari, Chrome or Firefox.
2. Drag the PDF from the Finder onto the page, or choose Select a file.
3. Type a password in Password. It must be at least 6 characters.
4. Type it again in Confirm password. A mismatch is shown under the field as you type.
5. Choose Protect this PDF. The button stays disabled until both fields match.
6. Download the protected copy, which has "(protected)" added to its name.
7. Open it in Preview to confirm it asks for the password, then store the password somewhere safe.

Before the result appears, Deckle checks that the new file refuses an empty password and opens with yours.

What the password does

The password is needed to open the PDF. Without it, the file cannot be read, in Preview or in any other app. Deckle uses AES-256, the strongest encryption the PDF standard defines.

Deckle sets one password for opening the file. It does not set separate printing or editing restrictions, so anyone who can open the file can also print it. If you need permission restrictions, Preview's owner password (below) offers them.

A forgotten password cannot be recovered by Deckle or anyone else. Keep the unprotected original until the password is stored in your password manager, such as the Passwords app.

Choose a good password

• Use a passphrase. Four unrelated words, such as harbour-tulip-ledger-nine, are easier to remember and harder to guess than a short word with symbols.
• Don't reuse your email or Apple Account password. The PDF password will be shared with the recipient.
• Send it separately. Email the file and text the password, so one intercepted message does not open it. See how to share a password-protected PDF.

Password protect a PDF with Preview

Apple's page Password-protect a PDF in Preview on Mac gives the steps:

1. Open the PDF in Preview and choose File > Export. Give the file a new name if you want to keep an unprotected original.
2. Click Permissions and select Require Password To Open Document. Enter the password and verify it.
3. Enter an Owner Password. Actions you leave unticked, such as printing, then need the owner password.
4. Click Apply, then Save.

Preview's Locked setting is something else. Apple's page Lock PDFs and images in Preview on Mac describes it as stopping a file from being edited or deleted. That guards against accidental changes, not against someone reading the file.

Change or remove the password later

To change the password on a file protected with Deckle, open it in Unlock PDF with the current password, choose Remove the password, then protect the unlocked copy with the new one. Deckle cannot add a password to a file that already has one.

Tips

• Remove metadata before you lock the file. Protection keeps the Author and Title properties. Clear them first with Remove PDF metadata; see how to remove metadata from a PDF on a Mac.
• Merge first, protect last. A protected PDF cannot be merged. Combine files with Merge PDFs, then protect the result.
• Don't protect files for upload portals. Most online forms cannot open protected PDFs.

Frequently asked questions

How do I put a password on a PDF on a Mac for free?

Use Password protect PDF in your browser, or Preview's File > Export > Permissions.

Is my password sent anywhere?

No. The PDF is encrypted in your browser. The password is not stored or uploaded.

Can I stop people printing the PDF?

Not with Deckle, which sets an open password only. Preview's owner password can restrict printing.

Can I protect several PDFs at once?

No. Protect each file in turn, or merge them first and protect the combined file.

Related tools

• Password protect PDF to add an open password
• Unlock PDF to remove a password you know
• Remove PDF metadata to clear properties before locking