To reproduce, on a clean XE:
On the console you'll get gigabytes of logs and if you succeed in scrolling enough you'll find some NPE.
In the end you'll see the Panel Wizard being displayed...
There are several things to fix IMO:
- Reduce the logs on the console. It's just huge.
- Find the page that breaks the PDF export
Note: I've tried to run the same PDF export query on platform.xwiki.org's DevGuide and got a similar result: logs in the console, you don't get the PDF but instead get some page displayed.