STEVE HUFF a followup suggestion - a similar program, CocoaBooklet, has the option of limiting the size of the booklet produced. for example, if you're printing a 200-page document and you ask CocoaBooklet to limit the booklet size to 100 pages, you get two separate PDF files, one containing pages 1-100 and the second containing pages 101-200.
this sort of functionality could also address the request about creating 16-page bundles for hand binding.
finally, i would appreciate the ability to set an internal gutter margin, to make space for binding.
(Version 1.4)