Hi Shabbir,
You can use CRM actions to trigger fax documents from CRM.
For this to work, you first need to have smartform created for the fax content. a class and method need to be created for creating the smartform at runtime.
Next you need to define an action profile and action definition. User action type as "smartform fax" and you can make this action partner dependent if you want system to automatically pick the partner and retrieve the fax number maintained in partner's BP.
SAPConnect settings need to be completed by your Basis team to send the message to fax.
Hope this helps.
Regards,
Divya