If you go to the URL you use to import the WSDL, you will open the WSDL. I'd say either saving it and somehow making it available to the caller in a different location, or directing the caller to this location would be the easiest to get them the WSDL.

Update:

Assuming you are not running the app locally, the /ws-doc/ location should be reachable for the caller. If he is also using Mendix, he could use the usual URL import method from here to import the web service.

If not using Mendix, he can click on on of the published webservices at this location to see what a request to the webservice should look like as WSDL, as well as the format of the return by the web service.

From this he should be able to see the format of the request which his program should somehow generate (how this is done is up to the caller and depends on the application he uses) and use for the webservice call. Similarly he can use the example response to see what the response of the webservice will look like. What the caller then does with this response to use in his own non-Mendix program is again up to him.

I'm personally not sure either though how to generate an .xsd file from this...