How to get the document which is associated with a process having specific Guid value?

[C# Programming]

when a PDF file is opened, AcroRd32.exe is started automatically, and we get the GUID value of that adobe reader.
In c#, can't we get the document associated with the GUID value, I mean the total PDF file which is opened in adobe reader at runtime.
Here I'm struck up in code, can anyone suggest how to where I was missing something.
Acrobat.CAcroAVDoc AcroAvDoc;
Type AcrobatCAcroType;
AcrobatCAcroType = Type.GetTypeFromCLSID(new Guid("{CA8A9780-280D-11CF-A24D-444553540000}")); // This CLSID is of adobe reader's.

///////Here I think I'm missing something

Object obj = Activator.CreateInstance(AcrobatCAcroType);
AcroAvDoc = (Acrobat.CAcroAVDoc)obj;
I think I can get the full PDF document with AcroAvDoc.GetPDDoc();

Thank you...