pdfInspect offers a flexible GUI interface for viewing the internal structure and content of a PDF file. Wraps the Apache PDFBox library; example of application built with Superficial http://superficial.sourceforge.net
This project provides a toolkit and framework based on PDFBox for document analysis of PDF files and performing custom conversion tasks and is published under the Apache licence. A GUI is also included, and is published using the GPL licence.
Automatically embed Wikipedia topic information into PDF documents via pop up annotations. This relies on the Wikipedia Miner service that is also available on Sourceforge.