JPedal is a pure Java library providing viewing and extraction functionality for PDF files and includes lots of code samples showing how to integrate it into custom applications. It is used by clients ranging from the world's biggest companies to single developers.
JPedal is developed by IDRsolutions (a UK based company) and is available in both Open Source and Commercial versions. The Open Source version provides some useful sample code for using the JAI libraries.
PDF has very demanding image requirements, and JPedal makes extensive use of JAI to convert different types of raw data streams into images and for converting images into TIFFs and JPEGs for image extraction.