When I open existing files in Word 2016, they open in some unusual extra wide page width. They were saved in "normal" 8 1/2 x 11 format but they now open in some format greater than 18 inches. When I try to reset the page layout to 8 1/2 x 11 it won't reset to anything other that the default that everything keeps opening in.

How can I get the default back to 8 1/2 x 11 and resave my files in the proper 8 1/2 x 11 format?