A messaging system supports a presentation session with participants of the presentation, a presenter and one or more audience members. The message system allows the participants to share messages and documents via respective client/mobile devices. An application on each mobile device allows the audience member to peruse and comment on document portions (e.g., pages, images, or slides) being presented. The presentation sequence for the document portions can be managed by the presenter, or document perusal can be decoupled from the presentation sequence to allow audience members to focus on past or future document portions. Comments of the audience member or other participants can be linked to corresponding document portions.