Add vinegar, apple juice, canola oil, dijon mustard, and honey to food processor or blender and pulse until well-combined. Stir in poppy seeds and add salt and pepper to taste, if desired. Reserve 1/4 cup of the dressing and set aside.
Add red leaf lettuce and walnuts to large bowl, drizzle the remaining dressing over the top, and toss to coat well. Divide the lettuce among eight individual salad plates or bowls. Add pears to the large bowl and toss them with the reserved 1/4 cup dressing. Spoon pears evenly over the eight salads.