1. Rinse and drain lettuce leaves; wrap in towels, enclose in a plastic bag, and chill at least 15 minutes or up to 2 days.
2. Rinse shrimp with cold water and drain. Rinse and stem tomatoes; if larger than 1/2 inch, cut into quarters.
3. Coarsely chop nuts. Rinse pears, core, and cut into 1/4-inch-thick sticks; in a bowl, mix cut fruit with lemon juice.
4. Mound lettuce on plates or in bowls. Over lettuce, evenly scatter shrimp, tomatoes, and nuts. Top equally with pears. Ladle dressing to taste over salads and sprinkle with pepper.