DocuSign Inc. raised its expected IPO price range to between $26 and $28 a share in a Wednesday filing, up from between $24 and $26 previously. The company, which allows companies to send out legally binding documents and obtain electronic signatures on them, is expected to price its IPO late Thursday and see shares begin trading on Friday. Based on 136 million shares outstanding at the end of January, the company would be valued at $3.5 billion if shares priced at the low end of the new range and $3.8 billion if shares priced at the high end. DocuSign is offering 16.1 million shares and selling stockholders are offering another 5.6 million.