lowering output logic levels
A voltage divider could be made to work fairly well if the device with the low level input has a high impedance and thus does not load the voltage divider. 

If the target device is of a lower impedance nature or presents different input impedance depending upon the input voltage level then it would probably make sense to use a voltage comparator to detect the high and low thresholds of the signal from the RS485 device. As long as the comparator was an open drain device with an output low saturation level of less than 150mV you could then connect the comparator output also to a suitable pullup resistor.