They forgot to close the layers and flatten the final image. The datestamp layer floats above the remaining layers and that screwed the pooch for the kenyan and his fellow fraudsters. See, if you re-import the Adobe pdf in Adobe Illustrator it contains the history of layers and commands, the investigators unlocked the layering fail on the actual datestamp layer. This is a forgery.
There may be an explanation for the apparent forgery. Has the sheriff and his posse considered that the birth certificate, draft card, social security card and other documents may be fake, but also accurate.