We are back to my previous Feb 12 reply.
Check if Automator has a Documents Library introduced by Microsoft 365 or either Office 2019/2021 for Mac. If it does, you will need to use the Open Word Document, and the Find and Replace Text in Word documents actions, as shown in that preceding link. The only other means of externally changing content in a Word document would be via AppleScript if Microsoft provides scripting dictionary support for that purpose. No other workflow or scripting solution can do this, other than some incantation of Word basic.
I do not have Word installed, so I cannot create and test an Automator or Shortcuts workflow solution to Find/Replace text in a Word document. None of the scripts that I have posted can perform find/replace in a Word document. Converting the Word document to PDF won't solve batch-changing text in Word documents, and introduces separate programming challenges.