Layer7 API Management

We have a requirement to create a policy end point on gateway 9.0

That takes a couple of parameters and returns a pdf as binary

The policy end point calls a backend web service that returns a pdf as a binary.

Question is -Within the policy end point,  when the backend web service responds , is the pdf as binary available in response.mainpart variable ?

And do we simply pass back response.mainpart in return template assertion so that the pdf is returned back in the policy end point to the calling application ?

How do you call the backend webservice? if you use route via http assertion and you don't need to modify anything on response, then you don't need to do anything after route via http assertion, the route via assertion will return the response (with pdf)  to requestor