Apple Preview darker than Acrobat Reader?

I was getting very frustrated that even though I had followed the color management instructions, when I exported to a PDF, most of the images for my book were noticeably darker. I was using Apple OS X Preview to view the PDF, so on a whim, tried opening it in Acrobat Reader, and everything looked much better. This only makes sense, since it is the same company as Photoshop and InDesign, but I was curious if this was a common problem and if there was a reason for the difference.

Thanks