Place pork into a large lidded container.

Blend pineapple juice, onion, vinegar, orange juice, lime juice, garlic, chipotle peppers in adobo sauce, sazón, chili powder, salt, cumin, and black pepper in a blender until smooth. Pour over pork and toss until all meat is covered. Seal the container and marinate for at least 8 hours or up to 24 hours.

Turn on a multi-functional pressure cooker, select the Sauté function, and add vegetable oil. When hot, add marinated pork and brown on all sides, working in batches if necessary, about 5 minutes per batch.

Turn off the Sauté function. Pour in reserved marinade, then close and lock the lid. Select high pressure; set the timer for 35 minutes. Allow 10 to 15 minutes for pressure to build.

Release the pressure using the natural-release method (about 10 minutes), then use quick release for any remaining pressure (about 5 minutes). Unlock and remove the lid.

Set an oven rack about 6 inches from the heat source and preheat the oven's broiler. Line a baking sheet with aluminum foil.

Transfer pork to the prepared baking sheet. Coarsely shred the pork, removing and discarding excess fatty chunks. Spread meat evenly onto the baking sheet and add pineapple chunks.

Broil in the preheated oven until the tips of the meat and pineapples are beginning to get a little brown and crispy, about 5 minutes.