Prince Processor

I have been trying to use princeprocessor to attack a pdf hash. It starts up fine but just stops on a blank line.
The command line i'm using is the following:
pp64 < english.dict | hc64 --session=prince -m 10500 hash.txt -r=prince_optimized.rule -w3

I have searched the other threads can fine no example usage for princeprocessor other than what I have shown.

I seem to be missing something here that is not blatantly obvious to me.  The process stops after it shows 
"Starting attack in stdin mode. . ."  It seems to be waiting for something. . . . 
Someone in a thread said they had the same problem and the response was that it was waiting for something to do.

What?  What am I missing here???

Anyone's assistance would be appreciated.
/r

I've tried adding a min and max password length, same issue.