In a pot of boiling water, add the dried guajillo and ancho chilies. Let them soak for about 10 minutes until softened.
Once softened, drain the chilies and set them aside.
In a blender or food processor, combine the softened chilies, garlic, pineapple juice, orange juice, vinegar, oregano, cumin, paprika, cinnamon, and achiote paste.
Blend until you achieve a smooth, thick marinade. Season with salt and pepper to taste.
Place the thinly sliced pork in a large bowl or resealable plastic bag.
Pour the marinade over the pork, ensuring all the meat is well coated.
Cover the bowl or seal the bag and refrigerate for at least 4 hours or preferably overnight to let the flavors develop.
Preheat a grill, grill pan, or cast-iron skillet over medium-high heat.
Remove the pork from the marinade and cook in batches, ensuring the meat is cooked through and has a nice char. This should take about 6-8 minutes per side, depending on thickness.
While the pork is cooking, grill the diced pineapple for a few minutes until slightly caramelized. This step enhances the sweetness and adds a smoky flavor to the dish.
Once the pork is cooked, thinly slice or chop the meat.
Warm the corn tortillas on the grill or in a skillet.
Place a few slices of the cooked pork on each tortilla, then top with grilled pineapple, chopped onions, cilantro, and a squeeze of fresh lime juice.
Serve the tacos immediately with extra lime wedges on the side for added zing.