please help me!

Hi all,
I'm new to this list and to docbook in general. I'm triyng to convert my 
first doc from docbook xml to a pdf. But I'm unable. it seems that on 
the xml produced by the docbook with the menu iten "show as a docbook" 
there isn't the DOCTYPE definition and also the DTD link. Why does it 
happen? Where do I am in wrong? Please answer me, I', thinking to leave 
bocbook... :-(

Renato