A single sheet, or three 2-sided sheets folded into a booklet?
Printed from your office printer, or sent out to a print shop?
If its three sheets to be printed in-house, save as a pdf, and use booklet printing from Acrobat.
Believe it or not, they actually want a single two sided sheet to be eventually printed at a print shop.
There are a couple of ways to make the pages fit in their existing format, but unless all the text is at least 12 pt on the original, it will not be very legible in the new version, where it is shrunk down to just over 50% size.
I think the only way to have a chance of making this look (and read) decently is to make a brand new layout of four 8.5 x 11 sheets, and condense your 12 pages down fit into four.
That's the only thing I could think of as well - thanks for your input.