While running the KDE Advanced Text Editor (Kate), you can speak the text displayed. First ensure that Jovie is running and enable the KTextEditor Jovie Text-to-Speech Plugin in Kate's settings dialog. Highlight the text you want spoken and choose → on the main menu. After a moment, the highlighted text should begin speaking.
You do not have to first highlight text. In this case, the entire file will be spoken.
This also works when Kate is running embedded in another application, such as Konqueror or Quanta.