Password Protect Office document
Open the Word document that you want to protect your password and click on the option 'File'. Towards the right hand side you will see the option 'Protect Document'.

Click on the option and you will find new options are highlighted below
Mark as Final
Encrypt with Password
Restrict Editing
Restrict Permission by People
Add a Digital Signature

Our particular interest lies in protecting the document with a password option with password encryption. So, choose the second option from the top.
Once completed, the Encrypt Document dialog box appears. In the Password box, type the password. Remember, if you fail to remember the password, Microsoft will be able to retrieve the password is lost or forgotten, so keep a list of passwords and corresponding file names in a safe place.

Choose a strong password, then select OK.

Enter the password you want in the Confirm Password window and click OK.
You will now see the new permission required.

Hope that may help!
Read more: http://www.windows8kita.com/2013/04/tips-password-untuk-melindungi-office.html