Adobe adopted U3D for its 3D format for PDF. That was a pain, because of the dearth of U3D translators. With the next release of Acrobat 3D (due Q1 next year), Adobe is adding TTF's PRC format. It can read all the major 3D formats, displays Product Manufacturing Information (dimensions, tolerances, notes, etc), and can highly-compress files.
Acrobat 3D will export drawings in STEP, IGES, and ParaSolid formats. That means the product becomes a US$995 3D CAD drawing translator. More details in this week's upFront.eZine. Subscribe for free.