I prefer a paper catalog if it is available. Since I work in the graphic industry I certainly promote print
The second thing you should have is of course a PDF-file of the catalog for download. The full catalog and then maybe sections of it.
One thing with PDF-catalogs is that you can make them interactive and searchable if you put in some effort in it. Sorry to say but that is seldom the case, most companies only save the print catalog as a PDF without make use of the PDF-formats advantages. On such example is Classic Industires 700+ pages catalog. The registry can be made clickable so that you will go to the page in question with one simple click.
If you like I can help you out with some questions regarding the catalog and PDF, you know where to find me
Since i am overseas it is easier to download a PDF and print it myself on my laser, or just look at it on the monitor.
Jan