Have wanted to mean --1. You have an ADC device which provides 12-bit data; you want to acquire this data using Arduino UNO. If so, you can always do it.OR2. You have a sample of analog signal which you want to digitize into 12-bit parallel format using Arduino UNO. If so, you can't do it. You need Arduino whose internal ADC has 12-bit resolution.
Because, I could not understand the underlying message of your original post; I have wanted the clarification through two queries of my Post#1. In response, you have referred me to a link; is it the right thing that you have done?
What sensor are you using? IIRC the linked ADC uses fixed internal reference. If the sensor is ratiometric it would be better to use another ADC.