The simplest approach is to use two resistors. Connect a resistor between the device output and the Arduino analog input (call this resistor R1), and another resistor between the analog input pin and +5V (call this R2). Then the voltage Va at the pin is related to the voltage Vo from the device like this:
(5 - Va)/R2 = (Va - Vo)/R1
Va = (5*R1 + Vo*R2)/(R1 + R2)
If you choose e.g. R1 = 10K, R2 = 22K then you will find that this maps your -2V to +4V output to a voltage range that can be measured by the Arduino.
[EDIT: after I composed this, you edited your original post, changing the voltage range that you want to measure. So you may want to change R2 to better suit that voltage range.]