It is safe to assume that handing out this littera-trash without express permission from the store or property manager is forbidden. Not only that, but it disrupts business--these stores are in business to sell products that people want and need, not to serve as targets for Jehovah's Witlesses to go around hassling customers (who might then go to another store instead).
In fact, it is the widespread tendencies for Wal-Mart to allow the witlesses to set up booths that had a lot to do with my going to L.L.Bean instead for my purchases of clothing, and to other stores for other things. It is impossible for the witlesses to set up booths online. True, I do pay more for the product (and get better product), and I pay for shipping and handling (with money and shipping time). But I don't have to worry about those busybody witlesses hounding me to go back to the Kingdumb Hell.