I can’t remember when Adam Hyde first suggested to me that CSS regions might be a viable way to produce PDFs for scholarly communications but it seemed like a good idea at that time and, I think, it still does. CaSSius is my implementation of that idea.
To back up a bit, at the moment in scholarly communications, the production stage usually involves creating a PDF and XML copy in tandem, perhaps using a tool like eXtyles and a process involving Adobe InDesign.