get annotation coordinate value from acrobat pdf viewer using C#

Why? PDF is never the original source of information. Using it as a source, not for human's reading, is always some misuse of technology.
Some 3rd parties used to develop specialized solutions to overcome some situations when there is no other way. I call such business nothing but acting as a parasite on someone's stupidity, or so when a business system goes crazy. Are you working for such company? If not, you should think if this is really needed to do.
—SA