* Exxon Mobil shares rise after results beat Wall Street forecast
* Indexes on pace for strong monthly gains
* Chicago PMI well above expectations
* Jobless claims fall slightly less than expected
* Dow up 0.2 pct, S&P 500 up 0.3 pct, Nasdaq up 0.4 pct
By Luke and Swiderski
NEW YORK, Oct 31 (Reuters) - U.S. stocks edged up on Thursday, though trading was subdued a day after a Federal Reserve policy announcement that kept its stimulus plan in place.
While Thursday's rise was modest, stocks were headed for strong gains in October. The Dow was up about 3 percent as the month drew to a close, while the S&P 500 was up about 5 percent and the Nasdaq rose 4.5 percent.
Shares of Exxon Mobil Corp, the world's largest publicly traded oil company, helped support the Dow and S&P 500, rising 1.7 percent to $90.50 after the company reported adjusted third-quarter earnings that beat expectations.
The U.S. central bank on Wednesday said it will keep buying $85 billion of bonds per month, noting weaker economic signals.
But it removed a phrase from a previous statment expressing worries about credit conditions after a spike in bond yields, which investors interpreted as a sign the Fed could begin tapering earlier than expected.
"The Fed removed that language, and that leaves tapering on the table for December," said Michael O'Rourke, chief market strategist at JonesTrading, referring to the Fed's eventual trimming of asset purchases.
The Fed's accommodative monetary policy in recent years has contributed to stocks' rally, and investors worry about the timing of a pullback by the Fed.
The Dow Jones industrial average inched up 27.50 points, or 0.18 percent, to 15,646.09. The S&P 500 added 4.84 points, or 0.27 percent, to 1,768.15. The Nasdaq Composite rose 13.75 points or 0.41 percent, to 3,998.89.
Expedia jumped almost 18 percent to $58.61 and ranked as the S&P 500's best percentage gainer on the S&P 500 a day after reporting third-quarter earnings that exceeded expectations.
Limiting gains, Visa Inc lost 2.9 percent to $197.97, making it the biggest drag on the Dow a day after the world's largest credit and debit card company reported a 28 percent drop in quarterly profit.
Thursday's economic data was mixed. A gauge of business activity in the Midwest execeeded expectations in October, while weekly initial jobless claims dipped in the latest week.
The Labor Department's October employment report will be an important source of clues about the economy and future Fed action. Until the figures, due Nov. 8, are released "we're going to drift. We need something to send us higher", said Brian Battle, director of trading at Performance Trust Capital.
Facebook reported strong growth in its mobile advertising business late on Wednesday, though it said it didn't plan to boost the frequency of ads shown to users. Facebook's stock was up 3.2 percent at $50.60.
Of the 355 companies in the S&P 500 that had reported earnings through Thursday morning, 68.2 percent have topped Wall Street's expectations, above both the 63 percent beat rate since 1994 and the 66 percent beat rate for the past four quarters, according to Thomson Reuters data.
Revenue has been mixed, however, with 53.6 percent of companies besting expectations, well shy of the 61 percent beat rate since 2002 but above the 49 percent rate for the past four quarters.