The full scale of the output of a DAC will often be dependent on the loading conditions. For example, in the MAX5215/7 datasheet it states in the electrical characteristics section the output voltage range under 10kOhm loading conditions is 0->VDD-0.2. This voltage drop is not always linear with loading. A full description of the output voltage vs loading is given in the typical operating characteristics section
Under higher loading conditions it might be necessary to include a voltage buffer at the output of the DAC to be able to use the full range of the supply voltage.