A computer implemented method and apparatus for sharing the contents of a presentation in a web conference through automated identification of documents for selective sharing with web conferences comprises launching a web conference in which an application or an entire desktop view of a conference presenter is caused to be rendered as content viewable on the displays of all conference participants. The method detects that one or more documents are being accessed by application(s) executed concurrently with the desktop sharing application and identifies documents having a supported format as including viewable content available for rendering to the display of the presenter. Automatically, or after presenter confirmation, the content is uploaded to a web server and converted into a format that can be distributed to and cached at the respective participant computers.