1. A document processing method comprising: incrementally, for each of a set of samples of a document, extracting local features from the sample; for each of the samples, computing a local score based on the local features extracted from the sample; estimating a global score for the document based on the local scores currently computed; and computing a confidence in a decision for the estimated global score, the computed confidence being based on the local scores currently computed; and outputting a decision for the document based on the estimated score when the computed confidence in the decision reaches a threshold value, the extracting of local features, computing the local score, estimating of the global score, and the computing of the confidence in the decision being repeated with additional samples until the computed confidence in the decision reaches the threshold value.