If the Developer tab is not showing in the ribbon, go to Word Options from your Office Button. Check the third box down on the Popular page.

Back to the ribbon. On the Developer tab, go to Protect Document and select Editing restrictions on the right. "Read only" will prevent others from changing the document. You will have to set a password, so be certain to write it down and keep it somewhere accessible to you.

Does this do the trick for you?