Heat the Instant Pot in sauté mode.
Trim the excess fat from the pork shoulder and cut into large chunks.
Add the oil to the instant pot and add half of the pork shoulder, turning to brown all sides. Remove to a clean plate and repeat with remaining pork.
Add the onion to the pot and cook until slightly translucent, 2-3 minutes.
In a small bowl, whisk together the chicken broth, orange juice, lime juice, garlic, cumin, salt, and pepper. Return the pork to the Instant Pot, and pour the sauce over the top. Place the lid on the Instant Pot and cook at high pressure for 30 minutes, then let naturally release for 15 minutes.
Remove the pork from the pot using a slotted spoon and shred. Strain the cooking liquid over a bowl, discarding any solids that are strained out.
Preheat the broiler. Spread the shredded pork on a foil-lined baking sheet, and pour about one cup of the cooking liquid over the top of of the meat. Broil 5-10 minutes, watching closely, until the edges of the meat are crispy and brown.
Serve warm in tortillas to make tacos or burritos or serve over salad.