iText consists of several jars.
The main iText release contains:
This project is hosted on http://sourceforge.net/projects/itext/ You can find the latest release here: http://sourceforge.net/projects/itext/files/iText/
In some cases, you'll need extra jars. These jars are bundled in a zip file here: http://sourceforge.net/projects/itext/files/extrajars/
For XML (and HTML) functionality, you need this jar:
This project is hosted on http://sourceforge.net/projects/xmlworker/
Finally, we also have a tool that can help you debug PDFs:
This project is hosted on http://sourceforge.net/projects/itextrups/