Saudi Arabia added four more banks to its secondary share offering of oil giant Aramco. The advisers began taking orders on Sunday for the sale, which could eventually raise up to $13.1 billion, 4 1/2 years after its record initial public offering. The Saudi government may sell up to a 0.7 percent stake in the world’s top oil exporter. The deal’s banks will take orders through Thursday, and the price will be the following day. The shares will start trading on Riyadh’s Saudi Exchange next Sunday. The investment banks added to the deal since it was announced on Thursday are Credit Suisse Saudi A…