For playback and simple printing, we recommend the free browser plug-in. With the free stand-alone player you can play the songs but not print them, while with the commercial NoteWorthy Composer program ($39 with free delivery in the United States) you can also print out the vocal score, with many more options to customize the printout than you get with the browser plug-in.
Just click on for the NoteWorthy icons
to get the NoteWorthy version of each song. This will give you the ability to print out the vocal score if you have the appropriate NoteWorthy plugin or program, or play the song and follow along with the lyrics.