How to identify if style of WSDL is document wrapped?

1. Part element is referring a element not type.
2. There in only one part in message.
3. Element referred by part should have same name as operation
4. Element's complex type has no attribute.

First two point holds good for WS-I compliant document style WSDL.

Can I have refer type inside part element in message for document style WSDL?

Well you can. WSDL will not be invalid. But if you are concerned about WS-I conformance then basic profile restricts you doing so. It only allows element not type to be referred in document style wsdl part element.