Thanks, I did not get that it was the input voltage used to power the board... I feel silly!
So, I read more carefully the page about it and it says:
Analog Inputs: pins from A0 to A11
The Due has 12 analog inputs, each of which can provide 12 bits of resolution (i.e. 4096 different values). By default, the resolution of the readings is set at 10 bits, for compatibility with other Arduino boards. It is possible to change the resolution of the ADC with analogReadResolution(). The Due’s analog inputs pins measure from ground to a maximum value of 3.3V. Applying more then 3.3V on the Due’s pins will damage the SAM3X chip. The analogReference() function is ignored on the Due.
Thus, if I want to measure a voltage from a photodetector, I have to be sure that this photodetector will never provide more that 3.3V. Is that correct?