From the Statement of Purpose:
In the GNU PDF Library, an individual can find a variety of functions that can be used to read and write PDF documents that are created in accordance with the PDF 1.7 specification. These functions include (but are not limited to) annotations, interactive forms, and other interactive features; as well as visualization, which involves retrieving bitmaps that have rasterized page contents. The library can also provide a good amount of help and support with creation of specific PDF subsets, as long as they conform to the following ISO standards: ISO 32000, PDF/X, and PDF/A
At the moment, no version of the library has been released, as the project is still in the developmental stages and has a great deal of work that needs to be done.
Please feel free to browse the Library Page if you are interested in learning more about this.