If you need a WINDOWS GUI interface...load and run pdflrfwin -- it works GREAT!
https://www.mobileread.com/forums/showthread.php?t=13135
for batch conversion of pdf to lrf, see..
https://www.mobileread.com/forums/showthread.php?p=97727
CACAPEE has done a great job creating and sharing this program!!!! Much thanks....