By preprocessing, we refer to all the procedures before the main task of a Document Image Processing system. It is a very wide area starting from image binarization, extending to noise removal, Geometric and any other transformations and could reach to segmentation, normalization, etc. Such preprocessing tasks are included in almost every Document Image Processing system. In this presentation, the evolution through time of several popular tasks is going to be presented. The combination of various tasks and their dependence on the system will be analyzed and evaluated. Our intention is to demonstrate how any given system could impose its preprocessing requirements, analyzing its involved problems and characteristics. Moreover, we will examine how the same preprocessing tasks can be shared between similar or related systems.