I'll use voltage level shifter between the devices and the DUE.
If you wish, you can operate the MCP4725 DAC at 3.3V supply voltage of the DUE. If so --
1. The resolution of the DAC would be 3.3/212 = 0.0008 V.
2. The full scale of the DAC would be 3.3V. That means that when 0b111111111111 (0xFFF) is written into the DAC, the voltage at the DAC's output would be 3.3V instead of 5V.