A family of Microsoft word processing software products for creating web, email, and print documents.
First confirm that Office is fully updated. Version 15.20.0 is current. Also, make sure your version of OS X is fully updated & check the mfr's web site to see if there is a more recent version of the driver software for your model.
Then try this:
- Go to Format> Document
- Click the Page Setup button
- Select the preferred paper size, click OK
- Click the Default button & confirm Yes
- Quit Word then launch to see if the setting stuck.
If not, go through the same process but select a paper size you don't want. After you Quit & Launch, do the process once again selecting the size to do want.
Reply with the details of your results if the problem persists.