A creasing device for forming creases in paper and bookbinding articles, said device comprising: a frame with a substantially horizontal support surface for supporting an article to be creased and feeding it in a substantially longitudinal direction; a pair of reciprocally facing tools, a stationary tool and a movable tool, placed on opposite sides of said support surface, wherein the stationary tool comprises a stationary member, integral with said frame and at least one displaceable member whose position can be adjusted in height relative to said stationary member; at least one elongated punch (7, 8) and at least one elongated recess (9, 10), associated with said movable tool and said stationary tool, in longitudinally offset positions; first actuator means acting upon said movable tool to move it toward said stationary tool and interact with the opposite faces (F S, F I) of the article, to form a crease; second actuator means acting upon said displaceable member for selectively moving it between a first end position (P 1) in which it is designed to interact with said movable tool and a second end position (P 2) in which it cannot interact with said movable tool; guide means associated with said stationary tool to guide said at least one displaceable member between said first end position (P 1) and said second end position (P 2); characterized in that said guide means are of the type having a curvilinear path contained in a plane (π) substantially perpendicular to said support surface and said longitudinal direction, said guide means comprising a cam consisting of at least one slot formed on one of said members (12, 13) and at least one pin associated with the other of said members (13, 12) for slidably insertion in a corresponding slot, said slot comprising a substantially horizontal first portion and a substantially sloped down second portion which is inclined relative to the horizontal, the portions defining respective sections of said curvilinear path. a frame with a substantially horizontal support surface for supporting an article to be creased and feeding it in a substantially longitudinal direction; a pair of reciprocally facing tools, a stationary tool and a movable tool, placed on opposite sides of said support surface, wherein the stationary tool comprises a stationary member, integral with said frame and at least one displaceable member whose position can be adjusted in height relative to said stationary member; at least one elongated punch (7, 8) and at least one elongated recess (9, 10), associated with said movable tool and said stationary tool, in longitudinally offset positions; first actuator means acting upon said movable tool to move it toward said stationary tool and interact with the opposite faces (F S, F I) of the article, to form a crease; second actuator means acting upon said displaceable member for selectively moving it between a first end position (P 1) in which it is designed to interact with said movable tool and a second end position (P 2) in which it cannot interact with said movable tool; guide means associated with said stationary tool to guide said at least one displaceable member between said first end position (P 1) and said second end position (P 2); characterized in that said guide means are of the type having a curvilinear path contained in a plane (π) substantially perpendicular to said support surface and said longitudinal direction, said guide means comprising a cam consisting of at least one slot formed on one of said members (12, 13) and at least one pin associated with the other of said members (13, 12) for slidably insertion in a corresponding slot, said slot comprising a substantially horizontal first portion and a substantially sloped down second portion which is inclined relative to the horizontal, the portions defining respective sections of said curvilinear path.