Recently I’ve meet the maintainer of the GNU PDF Project, a colleague of Ana’s, and once he told me about the project and its goals I thought it was quite interesting. My first thoughts were why another PDF project? Haven’t people solved that problem already? There’s a motivation page and there has been questions and answers about this on the project’s mailing list so I can’t explain it better than they do but one thing that seems important to me is the PDF 1.7 specification that the project wants to implement. That means having features in the free software world that are only available now in proprietary software, like interactive forms in a PDF.
It’s a very recent project, still with a small codebase and considered by the Free Software Foundation as a high priority project. Be sure to check it out, maybe it is that free software project you have been wanting to contribute in a while.