Carol, I would choose some kind of tool that helps you doing this. There are tools for LaTeX (a5booklet) and for Postscript (psbook) for this kind of page ordering. Doing that by hand in advance seems to be really hard, you shouldn't have to focus on such dumb stuff.
If you want to use scribus, do the layout with scribus, export to ps, use something like psbook to shuffle the pages into the right order and ps2pdf to get the Postscript into a PDF for printing. ...just my 2 ? Michael
