The smartFIX system, a commercial Document Analysis (DA) system, is introduced. It can be seen as a constraint solver over the domain of OCR alternatives. There are basically two types of constraints, database constraints and arithmetic constraints. The target of DA is then to optimize the constraint system, where the main challenge is the fuzziness of the OCR results. Efficiency is gained by a transition of the variables state from ‘soft’ to ‘hard’. Propagation is used to make sure that the result of the analysis is globally consistent. As an industrial application of (soft) constraints, smartFIX demonstrates the versatility of the generic constraints approach.