Increasingly, conference proceedings are made available on-line, rather than on a USB stick or CD-ROM. You can easily create such proceedings by creating a set of web pages, and then granting access to the pages via an access key. The conference then provides the access key to authors or registered attendees. This isn't meant to be highly secure - obviously, attendees can pass on the key to others. However, access is logged and users have to have or create EDAS accounts, so there is some deterrence to widespread sharing. The access key is configured under "Program, proceedings and BibTeX" at Conference:Configure. Users will be prompted to enter the key when they try to read the first paper; the system automatically remembers that the user has authenticated and will not prompt again for the access key.
Alternatively, if you're using EDAS to manage your conference registrations, you can designate specific registration options to include access to the papers.