Oh, nifty! This is more a demo of a PDF search engine that you could (in parts 1 thru x of the series) deploy to an intranet (for internal knowledge search) or internet (for general search), rather than a collaborative tool.
For handwritten/math symbols, I'm sure it wouldn't be too hard to integrate something. The Jina Flow [0] concept makes integrating new Executors [1] pretty easy.
I LOVE the testimonials on the site btw!