PDF Books graphics don't display on iPad

I subscribe to Safari Books Online and has downloaded some books in PDF format to my PC. The books displays correctly on my computer.I move the files to iTunes and sync them with my iPad 16 GB. But all the illustrations are blank when I open the books on my iPad.To read pdf files, try GoodReader app. It's the best app for viewing, reading, annotating, and moving pdf documents on the iPad.