Rinse pork shoulder under cold water and then pat very dry. Place skin-side up in a large roasting pan, right on the pan (not on roasting rack). Use a knife to cut slits into the skin and fat.
Combine the orange & lemon juice, vinegar, olive oil, onion, garlic, cilantro, red bell pepper, cumin, oregano, paprika, salt, and pepper in a blender or food processor and puree into a smooth paste.
Use your hands to rub the pork shoulder with the paste on all sides, pouring into any crevices and into the slits cut in the skin. Use all of the marinade. Cover pan with plastic wrap and let marinate a minimum of 2 hours and up to 2 days.
When ready to cook, remove from refrigerator and let sit at room temperature 30 minutes to take off some of the chill. Wipe off excess marinade from the skin of pork and pour water into bottom of pan so that it goes up about 2� on the side of the pork (leave the extra marinade in the pan). You can also use broth or a mix of water & both.
Preheat oven to 325�F. Cover roasting pan tightly with foil or pan cover and place in oven on lowest rack to bake for 4 to 7 hours or until very tender. (Smaller roasts cook less when larger roasts take more time. It's very difficult to "overcook" as long as you keep the heat low, the roast covered, and the liquid in the pan--you can even go down to 300�F if you want to be safe.)
Once meat is tender, remove foil from pan and let broil about 5 to 10 minutes, or until skin is crisp and crackling.
Transfer pernil to a serving platter. Serve pernil along with reduced pan juices, and a rice dish.