The only way to put them in portrait orientation when they are printed is to put them in portrait orientation before they are printed. I suspect you want the individual pages to be in landscape while the printed page is in portrait.

Even so, you will get:

x x x
x x x

rather than

x x
x x
x x

when it is printed. That is the nature of Word's print 6 to a page printing. It gives you a landscape printout of the original pages. This works well for 6 portrait orientation pages but not for 6 landscape orientation pages. If you put in a request to MS, they might add it, but I wouldn't count on that, the interface would become even more complex.

There are probably third-party utilities that will do what you want but I don't follow those.