Commenting post 398:
There is actually a way to embed "real" 3D data in a PDF doument using the U3D or PRC file formats. These can be directly embeded in a PDF document and can be navigated using a PDF viewer supporting 3D PDFs. At least Adobes acrobat reader can display those (but not on linux AFAIK). The PRC format seems to support CAD data directly whereas U3D seems only to support triangulated data. There is an U3D library available but unfortunately there is no free/libry library to create PRC files.