If I have a cropped image placed over a color background in CorelDraw, when I save as a PDF then open the PDF back up in Corel or Illustrator, the image takes on the background color it was on. Example: if I have a headshot of a person that was cropped to around their head, when saved as a pdf the image becomes square with the color around the head from whatever was behind the headshot. Is it possible to keep the raster image cropped when saving as a pdf?
What are your settings for PDF export?
Try PDF/X-1a and set compatibility to Adobe Acrobat 5 or higher.