A family of Microsoft word processing software products for creating web, email, and print documents.
If you don't change the paper size in the document, just feed A4 instead of A6, unless your printer is especially sophisticated, it won't know what size paper you've given it. The A6 may print at the top left or top center, but it will still be A6 size.
Selecting "4 pages per sheet" won't work. It will print an A4 page four times on an A4 sheet but, because it scales the original, it wouldn't work for A6.