What version of SketchUp are you using? Latest in your profile doesn’t answer the question.
Share the .skp file so we can see what you are working with. If you are exporting directly from SketchUp, the PDF will only have vector data. If you export from LayOut you can get raster and vector.
Maybe they could add that as a feature but it’s not supposed to. The PDF exporter in LayOut is better and you have much more control over what you get in the PDF.