if you're using a thermostat it should not feel hot. Your body temp is about 98 degrees, perhaps 95 or 96 at your fingers. You want the temp of the substrate to be about 84 or 85 degrees. Therefore if you touch it, it should feel cool or just luke warm. If you're not using a thermostat, some of those pads can heat up to about 135 degrees (or more). Newspaper needs about 360 degees to combust, so I doubt you'll start a fire with a heat pad, but you can and will kill a snake with those hot temps.
Just for your info, many years ago with my first Boa Constrictor, I used newspaper for my substrate and I did "Not" have a thermostat. My heat pad stayed at 137 degrees all the time. I had to make the newspaper about 3/4 of an inch thick to get the temp down to the 91 degree target I had in mind. But I did that for many many years with no fire and no problems.