In a mixing bowl, combine pineapple juice, achiote paste, white vinegar, minced garlic, onion powder, ground cumin, chili powder, black pepper, and salt. Mix well until smooth.
Add the thinly sliced pork shoulder to the marinade, ensuring all pieces are well-coated. Cover and refrigerate for at least 1 hour (or overnight for more flavor).
Preheat your grill or stovetop skillet over medium-high heat. If using a grill, soak wooden skewers in water to prevent burning.
Thread the marinated pork onto skewers, packing the meat tightly. Alternatively, you can grill the slices directly on the skillet.
Grill the pork for about 5-7 minutes on each side, or until fully cooked and slightly charred. If using a stovetop skillet, cook in batches if necessary.
Once cooked, remove the pork from the grill and let it rest for a few minutes. After resting, chop the pork into bite-sized pieces.
In a separate skillet, warm the corn tortillas over medium heat for about 30 seconds on each side, until soft and pliable.
Assemble the tacos by placing a portion of the chopped pork on each tortilla. Top with diced pineapple, chopped onion, and cilantro.
Serve immediately with lime wedges on the side for squeezing over the tacos.