How To Protect A Word / Excel / PowerPoint Document With Password
1. Go to File > Info > Protect Document > Encrypt with Password.
2. Type a password, then type it again to confirm it.
3. Save the file to make sure the password takes effect.
For Information:
How to Remove Password from A Word / Excel / PowerPoint Document
1. Open the document and enter its password.
2. Go to File > Info > Protect Document > Encrypt with Password.
3. Clear the password in the Password box, and then click OK.