Before you start doing this, always, always check with your printer. Not some sales guy, but the person who will actually be working with your file. Believe me, there are lots of places that absolutely hate designers doing their own impositioning, and would much rather use their own software. Sometimes trying to 'help' can be the most unhelpful thing you can do, both for yourself and the printer!
I should also point out that it's common practice these days to supply Quark documents in normal page sequence. If your printer says otherwise, I would suggest looking elsewhere.