Adding new elements to WSDL

I wnated to know if its posible to add elements to the WSDL file, that are not "ports, messages, binding...". I mean something like:
<definitions>
<types>...</types>
<messages></messages>
..
<service>...</service>
<something>something more</someting>
</definitions>

Whre something is a new element that I may declare in a new namespace.

I wanted to know too, what can be inside a <documentation> element.
thank you very much