Rhino still has problems reading grouped entities in PDF files.
As an example, when importing this datasheet, Rhino doesn’t import the illustration on page 1.
When I take this into Inkscape, I can export the illustration to PDF and then again into Rhino but once in a while I forget to ungroup all geometry in Inkscape and then Rhino doesn’t read all of it. I’m attaching both cases: grouped and ungrouped:
D 5600 - page 1 figure.pdf (36.1 KB)
D 5600 - page 1 figure-ungrouped.pdf (33.0 KB)
Related (old) wish: when importing a PDF with multiple pages, allow us to select which page to inport. I can do that in Inkscape but it would be nice to just have Rhino 
See: OT-Retrieving 2nd page from PDF as vector information