We don't yet have comprehensive docs for Asciidoctor PDF because we're still implementing a lot of the functionality.
You can add page numbers by setting the pagenums attribute:
$ asciidoctor-pdf -a pagenums README.adoc
The styling of the output will be controlled by the CSS-inspired theme system I've implemented (and still working on). To custom the content, you'll need to override the converter in Ruby (and eventually Tilt-based templates).
Asciidoctor PDF is still very much a work in progress. It works remarkably well for what it does, but there is still plenty of stuff it doesn't yet do. I encourage you to follow the issue tracker to see where we are with development:
https://github.com/asciidoctor/asciidoctor-pdf/issues
-Dan