I have a few questions about using images or pdf files as an underlay that I can draw line work on top of.  The images appear in the preview, but all I see after putting it in the drawing is a rectangle on the black screen.  Not sure what I am doing wrong?  I used to do this all the time in a different cad program I no longer have access to.  Is this feature available in the free version?  I downloaded it in 2015, but haven't updated to more recent versions.  I did however click on the button to begin free trial of professional version thinking that might be needed to get the feature - no luck.  I also tried turning my image I wanted to use into a pdf file, but that resulted in the same thing.  I understand that the pdf underlay feature is only on the paid version.  What is the difference between using an image and a pdf underlay?

Thanks,

Steve