I've just realized that MarketPress doesn't print packing slips or invoices... and then I searched the forums and this seems to be a feature that people have been requesting all the way back to 2009!!
This is possibly one of the most basic functions of a checkout cart system - so much so that I didn't even think to check if the system would have this function before I spent two months integrating it into my site... what gives?
Is there any kind of timeline on adding this functionality? The lack of this functionality will force me to find another solution for a checkout cart.