Knowing that your files are secure in Office 2013 gives you peace of mind, and Office 2013 includes a number of features you can use to ensure that the content you create is protected in the way that’s best for you. You might mark a file as final so that no one can make further changes; you could assign a password to the file; or you might add a digital signature or restrict editing to ensure that your content is safeguarded.
In the Office 2013 app, click the File tab to display the Backstage view.
Click the Info tab.
Choose Protect Document.
A list of protection options appears.
Click Mark As Final.
A message box informs you that the file will be marked as final.
Click OK to complete the operation ...