A plurality of folding stages, in which each folding stage carries out a folding operation, in steps, are provided. The folding stages each have a folding roller pair (2, 2'. . . 5, 5'), one each roller being located above, and one below the web or superposed webs (6) to be folded. The folding roller pairs, except for the first, are formed with matching groove - ridge profile. The folding roller pairs are offset, in coordinates in space, with respect to the coordinates of a first roller pair which has cylindrical shape, such that the spacing of adjacent folding stations, e.g. S1-S2, and the folding angle of the respective adjacent stations are related to the height offset of the downstream subsequent stage and the angular direction of a line passing through the centers of rotation of the respective rollers of the downstream pair in the downstream station, the relationship being so selected that the length dimension of a theoretical ridge line between adjacent stations corresponds at least approximately to the length dimension of a theoretical longitudinal line at the edge of the web between the same stations.