We now have a client-side PDF exporter (using the browser print feature) which makes it nice to layout items and provide a PDF export that is the best at matching what users see on screen. It supports all HTML elements and javascript. But it doesn't support features such as generating PDF forms for example.

In any case, I don't think we want this in XWiki Platform. If such a PDF Renderer was to be developed, it should be done in XWiki Contrib.