@unknownuser said:

If you want a PDF 'Image' of your drawing then export to Tiff or Png for the transperancy, open in Preview and save as PDF, that will contain the image file data.

This is a great way to get a transparent background in your pdf. However I find the difference here is that if one "exports" to pdf in the Pro version, the resulting image can be converted to vector objects in other programs. If one uses the method above, the image is only a bitmap pdf. This method shows shadows and other styles, whereas the "export" to pdf does not.