Tech Soft 3D, the creators of the Tetra4D product line has a free 3D PDF mobile reader for both iOS and Android. This application will read the 3D data that is contained inside a 3D PDF, however it will not read the entire PDF document, only the 3D. Find out more here.
There is an additional free app currently available for Android only that allows users to consume documents created with Tetra4D Enrich on Android devices. Find out more here.