Dear Imran,
you should note that annotations are rendered within the core library and should be stored in the PDF file itself.
If you would like to do an annotations sharing mechanism there would be a couple of paths:
1 - you should create your own annotation's engine that won't use PDF specification. You will render your annotation on a transparent layer over the pdf page.
Look at the text search with word highlight in the demo project, you'll se how to get coordinates and how to write over the page canvas.
2 - you should create a mechanism that extract annotations from a file, serialize it (in a json or something else), synchronize it within a sync server.
The second way will be the better as annotation will stay in the pdf file (performances, portability, compatibility outside your application) but will be the most difficult to be written.
Synching mechanism needs some knowledge: each note need a uuid (you should create the uuid and put it on the annotation... I could guess in the annotation name/description).
Synching would work in the background when the PDF is open on the device.
You should do a scan on the page (or overall the entire document) get the annotation list, get annotation name, synch with server, get new annotation from server, add them on the right page, save the pdf file locally not to loose such annotations.
This is the support we could provide you, it's tight to our tool itself.
If you need more support on getting/setting annotation you're in the right place.
My colleagues is checking your need to store/retrive annotation as serialized structure, will be back to you as soon as possible.
