A family of Microsoft word processing software products for creating web, email, and print documents.
had same problem in word 2013. what worked for me:
click the ruler at the top of the page to bring up "page setup" dialog.
the right margin was, for some reason, set to a really large number. like 20 inches or something.
changed it back to 1 inch.
similarly, paper size was changed to extreme width.
changed it back to standard 8.5 by 11.
no idea how these settings got corrupted in the first place.
Note that the original question is not about margin widths at all.