A knife folder (10) for folding sheet material (44) comprises a sheet feed (12) for feeding the sheet material (44) in a first direction, a folder for said sheet material (44) and a conveyor (54a-54g, 56a-56g) for conveying it and having at least one pair of rotating conveying components (54a, 56a), the axes of rotation (62a, 64a) of which are arranged in a second direction substantially perpendicular to the first. In its folding position the folder pushes the folded sheet material (44) between the conveying components of the pair(s) of conveying components. The sheet material is advanced as far as a stop (50). The folder has a knife (34) extending in a third direction substantially perpendicular to the first and second directions. The sheet material (44) can be conveyed in the third direction by actuating the conveying components (54a, 56a).