My view is that either you keep the literature in case you need it to refer to in evidence at a later date for any reason (ie something concrete to prove they are liars!).
Alternatively, shred it and put it in the recycling box.
It is a dangerous thing to hand / or sell these books to members of the unsuspecting public who may believe the rubbish that is written on the pages......imagine how bad we would feel if they became a baptized JW after buying a book from an exJW!!!