I'm looking for a software (or a site) [or even a combination of many] where two people can collaborate by reading a PDF where anyone can underline things and highlight them, while at the same time they can chat together. It would be great if it has MathJax or LaTeX support.
OS: Linux or Windows XP
I know no software or site that can make that. Google Docs is great but is only limited to *.ppt, Excel, and Word files and their equivalents.