What you're describing would often be done via a mailmerge using, for example, an Excel workbook or another Word document containing a table that has a separate row for each recipient and columns for the variable data (i.e. name, street address, suburb, state, variable text). When the merge is done, Word will create a document containing a separate letter for each recipient.
See:
https://support.office.com/en-us/art...f-932c49474705
https://support.microsoft.com/en-us/...etters-in-word