[azabua]

You can implement your own with canvas and PDFjs ... I did something back in the day with latex and java (yikes) ... but anything is possible ... now I would try socket.io whiteboard example so many could destroy the same PDF

[perrys]

Yep this is how I implemented it on Good Annotations. I used PDFjs to render the PDF as an image data string. I'll checkout socket.io but my understanding of socket.io is that it is websocket technology so i'm not totally sure what you mean.

Something i do want to figure out is server side rendering the PDF vs the client, because I beleive there is a lot of data lost using PDFjs i.e. signatures