Hi, I think your plugin is very nice, but I had some problems:
I tried it on two different blogs (different domains on the same server), but making the PDF I always get a single white page with only the header but no posts.
Both WP installations are in their own directory, i.e. the blog is in mydomain.org but WP url is mydomain.org/wp or mydomain.org/wordpress
I tried the plugin on a third blog, also on the same server, having WP installation on the "root" folder of the domain: there it works like a charm. Seems that having WordPress on its own directory prevents the plugin from getting the posts...