A very extensive tutorial can be found here. There's nothing in iText to create PDFs from JTables, though, so you'll have to write the conversion code yourself. That would make a good addition, so maybe you might consider donating code that does this to the iText project once you have something up and running (hint hint).
Well ... though as of now I have not been able to get a generic program for a report from a JTable, I have developed one for a TableModel. If that can be any help, I would love to contribute it to the itext community. Just tell me how i can do that.