Place a large cast-iron skillet over medium heat. Once skillet is warm, add oil, then dulse and liquid smoke. Toss to combine. Cook, stirring often, until dulse is crispy, about 5 minutes. Remove dulse from heat and season with pepper.
Slice pitas in half and toast lightly. Gently open them and divide avocado mixture evenly among all 8 halves. Divide greens, tomatoes, and dulse evenly among pitas and serve.