Q: We are very much interested in your PDFNet PDF library in order to provide a modern PDF output to our CAE-System
I think that PDFNet supports most our needs, but one question remains: is it possible to generate 3d-PDF files by embedding .u3d and/or .prc files?
A: Yes, you can use PDFNet to embed .u3d/.prc files among other things. As a starting point you may want to take a look at U3D sample project that is bundled as part of the SDK: http://www.pdftron.com/pdfnet/samplecode.html#U3D
For a relevent discussion, please see: https://groups.google.com/d/topic/pdfnet-sdk/7lB27MPpKhQ/discussion