When you use the "Book fold" setting, Print Preview displays the pages
consecutively (1, 2, 3, etc.) for ease in proofreading, format checking,
etc. But when you print, you will get the two pages that need to be together
to result in a correct printed booklet. If this is, say, an eight-page
booklet, then these will be 8 and 1, 2 and 7, 6 and 3, 4 and 5. If the page
you are printing doesn't yet have a corresponding page (or if the
corresponding page will be blank), then you might get only one half.
Note, however, that "Book fold" is not without its problems (known issues
are that it reverses Inside and Outside margins and sometimes doesn't print
the correct pages when you print selected pages or the current page). If you
get totally fed up with it, you can try one of the other options outlined at
http://word.mvps.org/FAQs/Formatting/BookletPrinting.htm
