[NTG-context] Arranging into Signatures?

(I am still using mkii, which I suspect may matter in this case) I am able to produce rather nice booklets on US Letter paper, printing double-sided two-up pages that fold into a booklet and using texexec --arrange to make it work properly. For documents longer than about 32 pages, it isn't really practical to fold in half. What would y'all recommend if I want to arrange the pages into signatures, each containing about 32 pages, that can then be somehow bound together? An external PDF rearranger might be an option, I suppose.