Pears: Place the pears, sugar, lemon juice, salt, and cinnamon in a large saute pan. Cook over medium-high heat, stirring occasionally, until the pears are soft and most of the liquid has evaporated, 10 to 15 minutes. Let cool.
Pecan Paste: In a food processor, finely grind the pecans and granulated sugar. Place the pecan mixture in a small bowl and add the water, orange zest, and salt. Mix just until combined.
Puff Pastry: On a lightly floured work surface, roll the piece of puff pastry into a 16-inch square. Cut into 4 rectangles, each 4 inches wide by 16 inches long. With a fork, pierce small holes all over the pastry. Place the rectangles on two baking sheets. Freeze or refrigerate until firm.
Preheat the oven to 375 degrees.
Place a second baking sheet or an inverted wire mesh rack on top of the puff pastry to prevent it from rising as it bakes. Bake until golden brown, 10-15 minutes. Cool to room temperature.
Assembly: Spread 1/3 of the pecan paste on one of the rectangles of puff pastry. Carefully layer 1/3 of the pears over the pecan paste. Layer two more pieces of pastry with the remaining pecan paste and pears in the same manner. Using a wide metal spatula, carefully stack these three pieces of pastry.
In a small bowl mix together the sugar and the cinnamon. Dust the fourth piece of puff pastry with the cinnamon sugar and place it on top of the stacked layers of pastry.Using a serrated knife and a gentle sawing motion, trim the edges of the napoleon so that they are even. In the same manner, cut the napoleon into 8 pieces and serve a portion on each of 8 plates.