Bring the pork to room temperature for at least 30-40 minutes before placing it in the oven.
Preheat the oven to 250°F.
Take the pork out of the refrigerator, remove the plastic wrap and place the pork in a large shallow roasting pan with the fat side up.
Add 1 cup of water into the bottom of the pan. This will prevent any drippings of the pernil from burning and keeping the pork moist.
Place in the oven on the lowest rack and bake for 5 hours, baste with juice every 30-40 minutes. keep the bottom of the pan from drying out. If you run out of juice, simply add more water, depending on how dry the pork is.
Remove the pan from the oven and increase the oven temperature to 450°F.
Place the pan back in the oven, and pour the vinegar and lime juice over the pork shoulder's skin. Cook until the skin is golden brown and crisp, 30-45 minutes. I like to tap the skin with a butter knife. You’ll know is ready when the skin is extremely firm and it has a dull thud when you tap it.
Once the skin is crispy pull the pan out of the oven, cover the pork with aluminum foil, and let it rest for 15 minutes. This will ensure the juices from the pan will be reabsorbed by the meat.
Then, transfer the pork shoulder to a serving platter. And now you are ready to dig in!