You can use Word's 'No changes (Read only)' editing restrictions for this. Simply mark the body of the document as an exception. Unless you mark the header as an exception too, users will be unable to edit it. In a multi-Section document, with different
Section headers, you'll need to avoid making the section breaks exceptions (or at least remove the exception status for them); otherwise, users will be able to delete them, which will also delete the associated headings.
Cheers
Paul Edstein
[MS MVP - Word]