Adjust two racks to divide the oven into thirds and preheat oven to 350º. You can use unbuttered and unlined cookie sheets or you can line the sheets with baking parchment.
Cut the butter the long way into quarters, then cut through all four quarters together, cutting 1/4 in. slices. Refrigerate.
Place the flour, baking powder, pepper and salt in the bowl of a food processor fitted with the metal chopping blade. Pulse once or twice to mix. Add the butter, pulse a few times and then process for only 4 to 5 sec, until the mixture resembles coarse meal. With the motor running, add the water through the feed tube and let the machine run for about 8 to 10 sec, until the ingredients just barely begin to hold together. The mixture should look like coarse crumbs.
Turn the dough out onto a length of plastic wrap. Fold the plastic over dough, press against the plastic to form the dough into a compact ball, then unwrap the dough and cut in half. Work with half at a time.
Lightly flour a pastry cloth and a rolling pin. Roll out the dough until it is very, very thin (1/16 in. or less). you may turn the dough upside down a few times while rolling and reflour the cloth and rolling pin as necessary.
With a four-pronged table for, prick holes about 1/2 in. apart all over the dough.
Traditionally these are cut with a plain, round 3 1/2 in. cookie cutter, but you can use any size and any shape cutter, or you can cut the dough into squares or rectangles with a pizza wheel or a knife.
Before you squeeze all the scraps together, see if thee are any pieces large enough to cut small squares, rectangles, triangles or crescents. (Cut the crescents with the same round cutter.) Reserve any scraps that are too small to cut.
Place the crackers on the cookie sheets. They can be placed right next to each other, as they shrink a bit during baking.
Roll and cut the second half of the dough. Any small scraps can be pressed together, rolled and cut.
Bake for 15 to 18 min, reversing the sheets top to bottom and front to back once during baking time to insure even baking.