Slice pork shoulder into 1-centimeter (¼ in) slices and place in a large dish.
In a medium bowl, mix achiote paste, chili powder, garlic powder, oregano, cumin, salt, pepper, vinegar, and pineapple juice until smooth.
Pour marinade over pork slices, toss to coat, cover with plastic wrap, and refrigerate for 2 hours to 3 days.
Place pineapple slices on the baking sheet. Skewer them with a wooden skewer through the middle.
Thread pork slices onto the skewer, leaving a 1-inch gap at the top. Add another pineapple slice on top.
Bake for approximately 1½ hours until pork is slightly charred and deep red.
Rest meat for 10 minutes, then carve thin slices of pork and roasted pineapple.
On tortillas, place pork, pineapple, onion, cilantro, salsa, and diced avocado.
Serve assembled tacos with lime wedges.