Shrink ADC signal from 5V to 1V?
A resistor divider is perfectly fine for the task. There is no real reason to reduce the voltage to 1V. If your ADC reference is 3.3V, make a resistor divider to reduce the voltage from 5V to 3.3V and have a full scale measurement. Beware to include the resistor divider tolerances into calculation, so you might end up having a resistor divider set up for somewhere between 0V and 3.2V. You can also do 0V to 3V in order to calculate values more easily in terms of math.