Checks whether the PDF contains objects with a blend mode other than one of the standard blend modes.
Blend modes determine how colors on different layers blend with each other.
There are 16 standard blend modes described in the PDF Specifications. They can be detected using the PitStop Inspector or the Select by blend modes Action. If new blend modes would be introduced (which is theoretically possible), this Action could be used to detect them.
For more information about blend modes, visit the Adobe website (http://www.adobe.com) or refer to the Help or documentation of your design application (Adobe InDesign, QuarkXPress, ...)