Set a password if you want people to know and enter a password before they can turn off document protection.
After you specify the type of restriction you want to use in the Protect Document task pane, click Yes, Start Enforcing Protection. In the dialog box that appears, you can apply a password, so that people you send the document to must enter the password you created if they want to unprotect the document.
Using a password helps to protect the format and content of your document when you collaborate with coworkers. The Protect Document features are ideal when you're working on a document with a group of trusted colleagues. However, this is not an encrypted password, and it does not secure your document against malicious interference.
Note You can also use Information Rights Management (IRM) to control access to your document (for more information about IRM, see Lesson 1). Click Restrict permission at the bottom of the Protect Document task pane to open the Permission dialog box. If you specify a combination of the features in IRM with features in the Protect Document task pane, Word enforces the most restrictive permission specified.