The SUp built-in PDF Exporter is for 'vector line work' only and doesn't support shadows etc - it's rather like a DWG export in that respect...
If you want to make a PDF of a scene with shadows et al [just as you might export an image file as a JPG or PNG] then you just download a free [or an inexpensive] PDF-writer.
It'll becomes an additional Printer - you simply print to that instead of your paper printer.
The PDF is saved - usually named after your model in a selected folder/desktop...
I use PDF995, but there's lots of others that are 'free' - see CutePDF, BullzipPDFprinter, PrimoPDF, PDFreDirect, PDFCreator etc - Google 'Free PDF Writer'...
The 3D PDF version doesn't take in the shadows either [I think?]...