When using overprinting the colour values of the overprinted object are added to those of the object underneath. This function is primarily used for black text to avoid blank streaks against coloured backgrounds.

When the overprint function is enabled, the background appears through the foreground colour. The text is printed on top of the background and with a slight plate offset no blank streaks are visible. The overprint function should be deactivated for white objects, because these objects will “disappear”.

Black areas that fully or partially obscure other objects are also problematic as different black values may arise depending on the underlying layer. Overprinting may be used as an “effect” (e.g. a shadow, by overprinting a light grey area). For some products with finish, e.g. partial varnish, the overprint function must be activated. Product-specific information can be found in the relevant data sheet.