Processing PDFs in Java

Anyone know of a Java library that extracts page images from PDFs?

Each page of the PDFs I am dealing with always just contains a single bitmap as they are all just scanned documents. I want an easy way to extract these images so I can display a thumbnail for each page...

I tried a library called Multivalent, but works intermittently for me. I've heard about something called J-Pedal, but I'm looking for something free first before asking this organization to spend the money (they are a non-profit trade association)

Thanks in advance,
Dave