Although the laser motors on a Sculpfun should be calibrated already, have you verified that a 1 inch square drawn in LightBurn produces a 1 inch square engraved on some cardboard? If not, then the axes need calibrating.
Are you taking the laser kerf into account? If not, measure the kerf and either embiggen the parts with an offset or apply a kerf offset to the entire layer.
And, as @MikeyH points out, maybe the photocopy / print / scan / trace / whatever sequence has done some scale damage along the way. Checking that will depend on what went on, but consumer-grade printers are notorious for nonlinear distortions we never notice on a printed page. 