Add some metadata fields that can be used to group song PDFs, like artist, genre, style, etc.
For bands or individual performers who take requests during their gig, it would be nice to categorize the songs in our library by artist, style, instrumentation, genre etc. Example #1: Somebody comes up and asks for a song by Journey, we could easily pull up the list of all songs in our list by that artist to choose from. Or Exampe #2: someone comes to the stage and asks for a foxtrot, it would be good to have a list of all the songs that would fit that dance style.
You can check out the keyword database which should help.