1. A method for training a handwritten document categorizer comprising: for each of a set of categories, extracting a set of discriminative words, from a training set of typed documents labeled by category; for each keyword in a group of keywords, synthesizing a set of samples of the keyword with a plurality of different type fonts, the keywords comprising at least one discriminative word for each category in the set of categories; generating a keyword model for each keyword in the group, parameters of the model being estimated based on features extracted from the synthesized samples of that keyword; computing keyword statistics for each of a set of scanned handwritten documents labeled by category by applying the generated keyword models for the group of keywords to word images extracted from the scanned handwritten documents; and with a computer processor, training a handwritten document categorizer with the keyword statistics computed for the set of handwritten documents and the respective handwritten document labels.