Microsoft Office has a powerful built in featture, that allows you to make whole document or only some parts of it read only.

To this press Tools->Protect document

Then a new pannel will appear at  the right part of the Office windows.

Then mark Allow only thistype of editing in the document. And select Read only.

Also you can make some exceptions for certain users.

After all press Yes, start enforcing protection.

You will be prompted for pasword (you may leave password blank) and press Ok.

That is all.