PDF Document Review and Commenting

I am planning to create comment functions on PDF files, which will be web based. Functions are,

Master user should be able to log in and upload a PDF file, and then assign numerous different users as reviewer.

As soon as master user add reviewer, no of layer on pdf document should be created & respective user can able to add comment on respective layer of same file.

All reviewer can able to see the comments on other reviewer layer but cannot edit, and able to write & edit comment on his layer only.

Master user can be able to edit comments on any reviewer.

Is there any open source tool to achieve above functionality?

Since you want to create a web based application to handle PDF documents, and create different layers over the PDF, you need to use a programming toolkit that supports these features over web. I know a developing SDK (leadtools) that supports loading PDF and annotations features in HTML5 and JavaScript. Annotations are markup objects usually used to add notes and mark up important materials on any image or document. You can find general information about Annotations in the following page:
http://en.wikipedia.org/wiki/Annotation
Note that the loading part might require using a REST service on the server side to load the PDF files and convert them to web-friendly format that can be viewed on the client side.
I searched internet and found the following online topics that might help:
http://support.leadtools.com/CS/forums/43011/ShowPost.aspx
http://support.leadtools.com/CS/forums/44274/ShowPost.aspx