Newspaper ink is plant based and non toxic. The worst that would happen is it would cause your BP to have ink on him.

If you are concerned with ink then either use unprinted newspaper you can get just about anywhere or just use paper towels. The difference between the two is not even worth concerning yourself with.

If you are concerned about humidity, you might want to use something better than paper such as coco fiber or cypress mulch.

As for holding heat, the UTH and a good hide on top of it will do far more for heat than any substrate.