Structurally, you will need to add support of SOAP 1.2 in your WSDL document.
Your 'abstract' WSDL part defines the types, messages and portTypes.
(I'm assuming here that you want to update your WSDL1.1 doc to add SOAP1.2 support for your existing service)
To support SOAP1.2 you will need to add SOAP1.2-compliant bindings and service definitions.
As an example, we have this port definition:
<wsdl:portType name="ServerSoap">
<wsdl:operation name="SomeOperation"> ...
You will need to add a SOAP1.2 binding section for your operation:
<wsdl:binding name="ServerSoap12" type="tns:ServerSoap">
<soap12:binding transport="http://schemas.xmlsoap.org/soap/http" />
<wsdl:operation name="SomeOperation">
<soap12:operation soapAction="..." style="document" /> ...
And a service:
<wsdl:service name="Server">
<!-- SOAP1.1 Service -->
<wsdl:port name="ServerSoap" binding="tns:ServerSoap">
<soap:address location="http://localhost:8080/Server" />
</wsdl:port>
<!-- SOAP1.2 Service -->
<wsdl:port name="ServerSoap12" binding="tns:ServerSoap12">
<soap12:address location="http://localhost:8080/Server" />
</wsdl:port>
</wsdl:service>
Note that the two definitions can co-exist and your service can remain backwards compatible with SOAP1.1. The clients will have to make the choice to use SOAP1.1 or SOAP1.2.
In practical terms, you could try generating the WSDL from the code you have, indicating Axis to generate bindings for SOAP1.2. I'm not an AXIS user, so RTM java2wsdl for a way to do that.