Using the free BookletCreator.com you can print any PDF file as a booklet. It saves paper because you get four pages per sheet of paper instead of one or two if you print conventionally. You can limit the number of pages per booklet for long documents — I recommend a maximum of 48 pages per booklet. This is an ideal method for those of you who like to print out the ebooks you purchase — it is very quick and easy.
There are very clear instructions on the site.
BookletCreator – is a free online tool that allows to create a booklet from a PDF document. It reorders pages so that after printing and folding the pages you get a small book.