Hi Hutto,
Just put a 10K resistor in series with the PWM signal and connect a 100nF (0.1uF) ceramic capacitor from the free end of the 10K resistor to 0V.
A DC signal, proportional to the PWM mark-to-space ratio, will be across the capacitor.
If that does not get the result that you want, just place more capacitors across the 100nF capacitor (but keep the ceramic capacitor connected): 220uF (0.22uF), 470nF (0.47uF), 1uF, 2.2uF, 4.7uF, 10uF, 22uF, 47uF, 100uF, 220uF, 470uF.
When the DC voltage is sorted, post what the DC voltage readings are and we can work out a suitable attenuator, if necessary, to get the voltages you need for your processor.
spec