9. Click the OK button.
Once you complete these steps, every time you open the document, you'll be prompted to
enter a password to decrypt its contents.
When setting up a password for an Excel, PowerPoint, or Word document, consider that
without a password it'll be virtually impossible to open the document, so make sure to keep
the password in a safe place.
How to Password Protect a Word Document on Mac
You can easily password protect a document on a Mac using Microsoft Word.
Caution: If you lose or forget your password, you cannot recover it. Without a password,
encrypted data cannot be restored.
Step 1. Open the document you want to add a password in Word. Then click "Tools". From
the drop-down menu, select "Protect Document".