Does not print duplex if Word document size is less than 8.5"x11"

[zuburg]

I have a word document with a document size of 7"x10" as I plan to publish an Amazon KDP book. When I try to print duplex (2-sided printing), it will just print each page in the document on a single piece of paper instead of printing 2-sided. Is the non-standard document size causing this? Is there a way to print two-sided with this document size? I'm just trying to print a draft to review.