All pleadings, motions, and other papers filed in a Commission proceeding shall be typed or legibly written on sheets of bond paper not more than 11 inches long or 8-1/2 inches wide, and each paper shall have a left margin of at least 1 inch and a top margin of at least 1-1/2 inches. All pleadings, motions, and other papers, excluding exhibits appended to the pleadings, shall contain a heading at the top of the first page and, excluding appended exhibits and written direct testimony for a public hearing, a certificate of service at the bottom of the last page.