Thanks to the help I've received from several members (particularly Ludovic) on this list, I have been able to put together an XWiki Groovy page that generates aggregate PDF's with a table of contents and an optional title page. This is a work in progress, but I thought it might be useful to others, so I've posted it here:
 
http://wwwxwiki.org/xwiki/bin/view/Dev/AggregateDocs
 
Regards,
 
Stephen