My HP Laserjet 1320 can do duplex printing, thus I can choose to print a multi-page document on both sides of the paper and so use half the number of sheets of paper.
However I wanted to be able to print a one page A4 document twice, once on each side of the A4 paper.
Googling and experimenting I found that if I chose double sided printing in Word (I'm using Word 2010) and then in the Pages to print box enter 1,1 it prints page 1 twice using both sides of the paper.
Similarly if I want to print the page as 2-up, A5 sized, on one side of the paper, I select single sided, A5 paper, and 2 pages per sheet, no change in paper orientation. Viola, I get 2 A5-sized copies side-by-side on one side of an A4 sheet.
Maybe this would be obvious to you, it wasn't to me, and it may just be a useful tip to others.