You could protect the document for forms, with no form fields.
Note, this is very weak protection.

General rule is that if someone can see a document, they can copy it. If they can copy it (even with screen shots or pencil and paper), given enough time, they can edit it. In a document protected for forms you cannot even select text.

Again, this protection is very easy to get around (takes less than 3 minutes) for someone who knows what to do.