Only tutorials are offered in PDF. The reason for this is that there currently is no system that really allows you to offer both HTML and *good-quality PDF* versions of docs without having to rewrite them or losing most of their format when creating the PDFs. Many formats and systems say they are able to do this, but as of today, this is simply not true. So we initially chose PDF.
Anyway, this said, we are currently looking for solutions for this and we hope to have HTML docs sometime soon... even if PDFs will not be as good :-(