Preheat the oven to 450°F. Line baking sheet with parchment paper.
Combine the sugar, salt and ground cinnamon in a small bowl.
Pour ½cup of the mixture on a big plate or wooden board. Unfold the puff pastry sheet onto the sugar and pour another ¼cup of the sugar mixture on top, spreading it evenly on the puff pastry. Make sure to evenly cover the pastry with sugar.
Roll the dough until its about 13"x13" square and the sugar is pressed into the puff pastry on top and bottom.
Fold the sides of the square towards the center so they go halfway to the middle of the dough, Then fold 1 half over the other half as though closing a book. There will be 6 layers.
Slice the dough into ⅜" slices and place the slices, cut side up on the baking sheet.
Bake the palmiers for 6~7 minutes or until caramelized and brown on the bottom. Then turn them over with a spatula and bake for another 3~5 minutes, until caramelized on the other side. Transfer to a baking rack to cool.