Cynosure Inc. of Westford is buying Palomar Medical Technologies Inc. of Burlington in a $294 million cash-and-stock deal. Cynosure said it gains complementary products, a stronger distribution network, new cross-selling opportunities, and 40 patents. Michael Davin, Cynosure’s chief executive, will be chairman and CEO; Palomar chairman and CEO Joseph Caruso will be vice chairman and president. The deal still needs shareholder approvals. Cynosure will relocate to Burlington. Its stock fell 4.75 percent.