Whisk the eggs with the salt and pepper, reserve. Heat a large, nonstick skillet over medium heat. Add the onion and bacon. Cook, stirring, for 5 minutes or until onions and bacon are browned.
Pour in the eggs. Cook, without stirring for 1 minute. Cook, stirring, for 1 to 2 minutes or until just set. Remove from the heat.
Use a small knife to cut halfway around the outside edge of each pita, fold back the top flap. Spread an equal amount of the ketchup all over the inside of each pita. Lay a portion of spinach over the ketchup. Top with a portion of the scrambled egg mixture, sprinkle with cheese.
Tuck the top flap of each pita inside, directly over the filling. Tightly roll the loose flap over the outside of each pita to completely enclose filling. Let stand for 5 minutes to soften cheese before serving.