Stocks inched mostly higher on Wednesday, enough to nudge the Nasdaq composite index to an all-time high. Markets continue to remain quiet ahead of Friday’s jobs report and the Labor Day holiday in the United States on Monday. The S&P 500 index rose 1.41 points, less than 0.1 percent, to close at 4,524.09. The Dow Jones Industrial Average fell 48.20 points, or 0.1 percent, to 35,312.53 and the Nasdaq climbed 50.15 points, or 0.3 percent, to 15,309.38. Small-company stocks did better than the rest of the market. The Russell 2000 index rose 0.6 percent. Technology and communications stocks made solid gains that helped lift an otherwise choppy market. Consumer staples also rose more than other sectors. Investors had a weak survey to work through from payroll processor ADP, which showed U.S. companies added jobs at a much slower pace in August than economists had anticipated. The weak report follows a …