If you want the documents to always update to whatever the preceding month is, it would be better to replace the dates with a field code that does the updating, rather than relying on macros.
To see how to do this and just about everything else you might want to do with dates in Word, check out my
Microsoft Word Date Calculation Tutorial, in the 'Sticky' thread at the top of the Word forum:
https://www.msofficeforums.com/word/...-tutorial.html
In particular, look at the item titled 'Calculate a month and year, using n months delay'. Do read the document's introductory material.
PS: I seem to recall providing you with a macro to change the dates as per your current request, in this thread:
https://www.msofficeforums.com/word-...edit-date.html