pfw is part of the pftools package, a collection of tools making use of generalised profiles for sequence analysis.

pfw computes new weights for individual sequences in a multiple sequence alignment using the method of Sibbald and Argos (1990).

References:
Sibbald PR and Argos P. (1990). Weighting aligned protein of nucleic acid sequences to correct for unequal representation. J. Mol. Biol. 216:813-818.