Mister Micawber, thank you very much for the warm welcome, and for your effort to help me! Forgive me for this question, it made no sense to me, either, and now i see why... I found the script of the movie, and originally they say "cut for sign", and not as in english subtitles i had (found on the net)
Anyway, the dialogue goes like this: Mattie: " who's the best marshal?"
'Sign' is any physical evidence -- tracks, scat, broken or disturbed foliage -- that indicate recent presence of an animal or person (presumably, the animal or person being tracked). To 'cut' for sign is simply to look for it; it does not imply anything about moving/not moving off the 'main trail.'