If your document contains sensitive information that you don’t want anyone else to see, you can encrypt the document so that no one can access its contents unless you give them the password you’ve created. You can further protect the document by allowing access to it but requiring a password to control who may make and save changes to the document.
With your document completed and saved, click the Office button, point to Prepare on the menu, and choose Encrypt Document to display the Encrypt Document dialog box.
Enter a password.
Click OK, enter the password again in the Confirm Password ...