A creasing device for forming creases (C) in paper and bookbinding articles (A), said device comprising: a frame with a substantially horizontal support surface for supporting an article (A) to be creased and feeding it in a substantially longitudinal direction (L); 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 and at least one elongated recess , 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 (A), to form a crease (C); 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 (T) contained in a plane (π) substantially perpendicular to said support surface and said longitudinal direction (L), said guide means comprising a cam consisting of at least one slot formed on one of said members and at least one pin associated with the other of said members 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 (T). a frame with a substantially horizontal support surface for supporting an article (A) to be creased and feeding it in a substantially longitudinal direction (L); 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 and at least one elongated recess , 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 (A), to form a crease (C); 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 (T) contained in a plane (π) substantially perpendicular to said support surface and said longitudinal direction (L), said guide means comprising a cam consisting of at least one slot formed on one of said members and at least one pin associated with the other of said members 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 (T). <EOS>