A family of Microsoft word processing software products for creating web, email, and print documents.
Try this -- In a new blank document go to File> Page Setup then in this order;
- Select the preferred printer from the Format For dropdown
- Select the preferred choice from the Paper Size dropdown
- Select Microsoft Word from the Settings dropdown
- Click the Default button
- Confirm Yes to the update
It wouldn't hurt to Quit the program... no need to save the blank document. On next launch you should find that your selected paper size is automatically set [File> Page Setup] for any new documents you create.