2D drawings in DWG files can be converted to PDFs by Acrobat X Pro. Converting 3D DWG 'model' files is not currently supported.
IAM/IPT conversion to U3D is possible, but not from within Inventor or Acrobat. You will need third-party software from someone like Tetra4D.
I'm a little confused though. Adobe seem to be pushing the 3D angle quite firmly, especially inthe release of Framemaker 11. So why do you need to buy very expensive third-party software just to get it to work?
Adobe was 'pushing the 3D angle' with Acrobat 9, but the focus has shifted somewhat since then.
Acrobat X will import the two native 3D model formats which are defined in the ISO32000 standard for PDF, namely U3D and PRC. Conversion of models to those formats is now the responsibility of external vendors. As both are non-proprietary standards is is/was hoped that OEMs would include export into one or both of these formats to their native applications (Catia, AutoCAD, Inventor, etc.) but to date this hasn't happened, so there is a commercial market for translation utilities filling the gap.