That is very unlikely possible. Shading of smooth surfaces is a function of all the facets of a mesh, a very special gradient. 2D vector graphics support primitive gradient types (linear, radial) and to limited degree higher parametrized ones.
The only reasonable way to represent complex smooth shading is to rasterize it (e.g. Inkscape rasterized unsupported effects to raster layers in PDF). As far as I know, SketchUp only has the option to export all raster or all vector (what you see is not hidden geometry, but the artifacts between the boundaries of the facets). Sketchup’s PDF exporter would need such an option for mixed vector/raster export.
You could of course hide edges and profiles and do a raster export, do a vector PDF export with hidden-line face style, and finally comose them in a single PDF file.