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
Hey! Your absolutely right, Apple has got down an awesome native PDF editor & annotator and that Windows do not have their act together for native apps.
The direction Good Annotations is taking however is to be able to do all of that collaboratively with other users. The stuff you see today is hopefully the first step.
Device compatability is obviously a tough one because there are so many different devices out there creating alot of edge cases. At the moment we're following the data to get things off the ground. Chrome & Desktop. We will be looking at touch support in the near future
Looking to jazz up pictures and screenshots in your blog or how-to guides? Good Annotations provides you online tools to quickly highlight any image area and make them standout out. You can easily add browser mockups and borders as well!