This sounds like a task for an automated mailmerge.
For the mailmerge basics, see:
https://support.office.com/en-us/art...f-932c49474705
https://support.microsoft.com/en-us/...etters-in-word
For the automation part, see
Send Mailmerge Output to Individual Files in the
Mailmerge Tips and Tricks thread at the top of the Mailmerge forum:
https://www.msofficeforums.com/mail-...ps-tricks.html