That's interesting. I've never had any problem printing .pdfs to large paper sizes. My standard is to use the standard page size of ANSI E, which is 34 x 44 inches. That's almost 3 feet by almost 4 feet. I use ERwin. Maybe that makes a difference compared to Study which I've never used.

I do have data models that take up more than one ANSI E sheet, but I lay out the tables so that related tables/areas all fit within an ANSI E sheet. It's been easy/usable for at least up to 4 ANSI E sheets. The .pdfs are usable and helpful. I haven't had to go more than 4 sheets, so I can't comment on usability for bigger.

The HTML option also sounds interesting. It sounds like you might be able to convey more data in one document going that route compared to simply printing up the data model. I have to print separate reports to make sure I have a file that shows all the meta data documentation I've added for the tables, columns, check constraints, etc.