First, it seems you are using an old form of iText. Look at http://itextpdf.com/ for the most recent version. You seem to be importing with "lowagie" which is the basis of my supposition.
Next, I don't see what line number you are erroring on, but you seem to be trying to use Flying Saucer to convert a rendered webpage to a pdf. Here is a little on that http://www.dayon.nl/content/xhtml-pdf-java-0
My preference (and experience) is that this will generally be fustrating, as what the PDF gets will not always match what you see on a browser - especially with free packages. You will get better results with purchased software, but there are frequently differences between how the browser servers it up and how the PDF rendering engine gets it. I think you will have better success in creating the PDF directly. You can see how to do this here: http://xpages.tv/xtv3.nsf/%24%24OpenDominoDocument.xsp?documentId=F0A8F4D764899C2A88257A05003F3375&action=openDocument
I have blog posts and sample databases http://www.bleedyellow.com/blogs/DominoHerald/entry/pdfs_from_xpages_via_itext_presentation_at_mwlug_2012?lang=en . You may want to look at some of my other posts on the subject as well.
Cheers,
Brian