Is there a way to create a 3D drawing from scratch? Basically would be similar to a CAD drawing, I suppose.
@Jody Wall
You can open a 3D PDF file in Revu that was created in another program, but there is no way to "draw" a new 3D PDF in Revu. However, you can convert a U3D or IFC file into 3D PDF via a plugin and then open that file in Revu. This article has more details on how you can use 3D PDFs in Revu.
Creating a 3D PDF