Including a 3rd party web page requires the drag and drop of a Web Page control (#PRIM_WEB.Page) from the Controls view onto a Web Page or Reusable Part. This equates to the embedding of an iFrame HTML tag in the final page. This control has a Source property that can be set to a URL.
#HTMLPage.Source := 'http://www.lansa.com/downloads/casestudies/robinson.pdf'
In this example the embedded frame will show a PDF supplied by the LANSA website.