Not sure how long we've been able to export to PDF from ER/Studio, but I don't think it worked well in the 99/'00 timeframe. The other issue is that you get into version issues with files as people store them in their machine, open the wrong one, etc.

I've always found a nice big diagram on a wall was the best reference. You can supplement it with a PDF or HTML, but a good central, easy to read point of reference is good.