I used to use a program called Drop Extract Images to take apart Aperture’s PDF book export file into its JPEG contents for uploading to WHCC for their books. But that program is now extinct under Mac OS X 10.7 Lion. But it turns out that the underlying Unix program works fine if you know how to use Terminal.
Here’s my post from a few years ago describing the situation.
And the Terminal fix is to call pdfimages -j, then drag the PDF file into terminal, then make a folder and drag the folder into terminal, and add a trailing “/”.