I suggest looking at:
https://www.msofficeforums.com/word-...er-footer.html. The macro there processes the document body, headers & footers in all documents in the selected folder. As coded, it replaces all terms from column A of the designated Excel worksheet with the corresponding terms from column B.
To process a single document, you could simply put it in a folder on its own. Alternatively, it could be edited to process only the active document.