Accepting literature of different religions

I live in the west, and every now and then, some Christian or Jew knocks on the door to give out pamphlets that promote their religion or an event related to their religion. I normally refuse the pamphlet but sometimes they put it in my hand, in which case I say ok and throw it out after I close the door. The people who give this stuff to me know I am a Muslim as I wear the niqab. Does my taking the pamphlet constitute kufr? Am I obliged to refute their religion to them right then and there at the door? If I don't, is that kufr?