The center of the paper is equivalent to the area of the position occupied by the text. As long as the margins are set above, the size of the center is155 mm * 245 mm. Because the size of A4 paper is 2 10mm*297mm, the width of A4 paper is 2 10mm minus the left and right margins and the binding line, which is 155mm, and the height of A4 paper minus the upper and lower margins is 245 mm. ..