Begin by thawing the Puff Pastry on your counter. It should take about 20 minutes.
Core the apples, and cut in half. Cut into slices (they should be fairly thin so they cook all the way through – use a mandolin if you have one).
In a large bowl, combine the cinnamon, brown sugar and salt.
Add the apple slices and mix well, making sure each slice is covered. Set aside for 5 minutes. Liquid will form in the bowl.
Roll out your Puff Pastry to desired size, and using a pizza cutter – cut the edges (to fold over later – see pics)
Drizzle a little of the liquid from the apples on top, then top with half of the pecans.
Add the apple slices in even rows, overlapping a little.
Top with remaining pecans.
Bake at 425F for 18-22 minutes, or until the edges are a golden brown.
Remove from oven and allow to cool.