The available options are designed to make the best use of the paper.
Especially using A sizes, where A5 is exactly half of A4 (rotated) and A4 is
half of A3, this makes sense. If you put three portrait pages on a landscape
page of the same size, you will have a lot of wasted space at the bottom.

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Suzanne S. Barnhill
Microsoft MVP (Word)
Words into Type
Fairhope, Alabama USA
Word MVP FAQ site: http://word.mvps.org
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> Right now, you can only select 2-pages-per-sheet under the multiple pages
> option in page layout. Any number of pages per sheet should be allowed to be
[quoted text clipped - 7 lines]
> link to open the suggestion in the Microsoft Web-based Newsreader and then
> click "I Agree" in the message pane.
http://www.microsoft.com/office/community/en-us/default.mspx?mid=c38df196-f47d-4
790-be80-7d21c58907b2&dg=microsoft.public.word.pagelayout