A small piece once in a while won't hurt but a steady diet of people food isn't the best for dogs.
Pepperoni is filled with salt and fat. A healthy dog should be able to eat a little and thee most they would get is some gas. However if the dog has some underlying health issues is can be bad. My husband gave a slice of pepperoni to one of our dogs and it caused pancreatitis. The vet bill for that one piece of pepperoni was $750.
Doesn't say anything I saw about Pepperoni but I give my Hound some of the outer crust here and there.
better than your dog eating ground up roadkill and pig intestines in commercialized dog crap. (dogs in the wild eat raw meat for crying out loud, a piece of cooked pepperoni would be luxurious to them)
Worth a look: