Key TakeawaysDocusign's first-quarter revenue only slightly beat analysts' forecasts, and its billings guidance raised concerns about future growth.The document-signing software provider's revenue was just 0.3% above analysts' consensus estimate.Shares declined even as Docusign boosted its stock buyback plan. Docusign (DOCU) shares fell Friday, a day after the provider of document-signing software only slightly beat revenue estimates and its billing guidance raised concerns about growth. The company posted ...