How to Set Print Scaling in Microsoft Word
See Microsoft Word: Tips and Tricks for similar articles.
If the paper size you need for printing is not the default of Letter, simply choose the desired paper size from the scaling option drop-down.
This feature works the same in all modern versions of Microsoft Word: 2010, 2013, and 2016.
On the Print page in Backstage view, under Settings, select the fifth drop-down that by default says Letter. Then select a scaling option. 
