Is it possible to download a file from a JSR 168 portlet ?

Issue

• Is it possible to download a file, example PDF, from a JSR 168 based portlet? Please provide some information on a facility for users to download the file? Ideally they should be available without the file having to be physically saved in the EPP server.
  Done some research and have found that serverResource() method appears to be the way to go, but this does not seem to be available for JSR 168 portlets.