Are you trying to create a protected document that is backward compatible
with earlier versions of Word? If so, first display the Developer tab (if
it's not already showing): Click the Office button, and click Word Options.
In the Popular category, select "Show Developer tab in the Ribbon" and click
OK. Then click the Developer tab. Use the Legacy Tools button to add the
form fields that you want. When you are done designing the form, click the
Protect Document button. Select "Allow only this type of editing in the
document" and choose "Filling in forms." Finally, click Yes, Start Enforcing
Protection. Type a password if you want to.