PDF is a meta format which may contain raster data (= pixels) as well as vector data (= geometry) even at the same time.
If the PDF contains vector data (which can be evaluated by zooming in or checking if picking the geomety is possible) you might want to use this exact geometric data instead of e.g. the raster-based screenshot by importing it to a graphics program as e.g. Adobe Illustrator or Corel Draw or free Inkscape (OS), export as DXF/DWG data and import into SketchUp (Pro only).