Modular web processing units may be physically and electrically assembled into clusters to perform various web processes (e.g. the production of paper forms such as invoices, checks, labels, etc.). Each module has a main process driver which is not directly coupled to a web drive mechanism. Rather, the web drive is program controlled so as to effect the desired web process at controlled displacement intervals along the web. Accordingly, a plurality of successive but different form lengths of depths can be accommodated as the web surface is sequentially processed. A system of such modules can be physically wheeled into position as individual units and electrically connected together by a suitable intermodule bus to rapidly configure a desired overall web finishing process. Examples of modules for unwinding web from a roll, for folding processed web, for printing and for perforation or cut-off are described. Each module has a mechanism driven by a motor for performing an action on the web, an encoder driven by the mechanism and a servo coupled to the motor and encoder, the servo being responsive to signals on the intermodule bus to control the speed of the motor so that the average velocity of the web through the module does not exceed the velocity of the web as it moves through the other modules of the line.