Unfortunately 3D PDF support is not on the short term Discover 3D roadmap.
However, we are intending on releasing a lightweight (less than 50MB download) and completely free Discover 3D Viewer, with no licensing required (therefore anyone can install and run it with no MI Pro/Encom products installed). This is scheduled to be released in tandem with the Discover 2012 release in June.
This will allow Discover 3D users to share their compelte, complex 3D sessions (including drillholes, block models, imagery, grids, etc) with any other person (clients, consultants, shareholders, etc), who can then visualise the session in its entirety, with full navigation and zoom fucntionality.
This viewer will allow your fellow team members, clients, contractors or in fact anyway at all to open and view your Discover 3D 2012 sessions, without them needing MapInfo Pro, Discover or Discover 3D installed.
The ease of transmittal and navigation for 3D PDF's is currently easier to handle for people outside your profession (People that do not understand Geology and do not work with the Encom Discover Suite).