Thank you, mstone, for your reply.
The reason for my initial post is the following from the Arduino description:
Warning: Unlike other Arduino boards, the Arduino Due board runs at 3.3V. The maximum voltage that the I/O pins can tolerate is 3.3V. Providing higher voltages, like 5V to an I/O pin could damage the board.
I have been unable to find out what voltage is presented by the Ultimate GPS Breakout, so I was trying to ensure that Due would not be damaged by an unexpected high voltage.