Hello.
I have 2 awesome plugins for ModX Evo... MultiFiles - add files like *.doc, .pdf, etc for each document. MultiPhotos - add images for each document.
how they work > http://www.polycom-ua.com/qdx6000
There is MIGX for Revo.
I think its kind of similiar, perhaps a bit more flexible, because configurable by input-properties (revo 2.1) or properties (before 2.1)