Reading full photocell range with ADC
The PDV-P8103 is only specified to a maxium of 100 lux. Direct sunlight is ~100,000 lux. Extrapolating the graph to this illumination I get ~250 &ohm; resistance, so the resistance range you need to measure is ~80k &ohm; (at 1 lux) to ~250 &ohm;. 

Resistance is inversely proportional to light intensity, so get a more linear response you should keep the voltage constant and measure current. This can be done by measuring the voltage across a small 'shunt' resistor in series. However this makes the output voltage rather small. 

If you don't mind a bit of non-linearity at high light levels then the shunt can be made larger, eg. 220 &ohm; with a 3.3 V supply should give you ~9 mV at 1 lux, 88 mV at 100 lux, 711 mV at 10,000 lux and 1.5 V at 100,000 lux. This can be converted to a linear brightness control value using a lookup table and/or piecewise linear curve fitting.