I have found a group label inconsistencies in the schematic. The naming of the AD inputs is flipped in the schematic.
Sources: Atmel SAM3X datasheet 23-Mar-15
Arduino DUE Schematic (download fom site dated ?)
Peripheral from pg.18
Datasheet Labels from pg.40
Pin # Peripheral Label (Datasheet) Label (Schematic)
78 PA16 AD7 AD0
79 PA24 AD6 AD1
80 PA23 AD5 AD2
81 PA22 AD4 AD3
82 PA6 AD3 AD4
83 PA4 AD2 AD5
84 PA3 AD1 AD6
85 PA2 AD0 AD7