Here's an example using the example web service from Hands on 1. When you click the button, the TWebBrowserControl navigates to the PDF endpoint. It displays an 'Open...' button to open the PDF. I am sure there are many other possibilities using hosted forms etc.
procedure TForm1.WebButton1Click(Sender: TObject);
begin
Browser.Navigate('http://localhost/flix/reportingservice/getcompanyprofile?aid=L13000088031');
end;