Adding comment on pdf layer (created using iTextsharp)

Question

I am new to this topic.
 
What i have done so far,
 
1) I have read existing pdf document
 
2) I have created copy of existing pdf using pdfStamper of iTextSharp
 
3) and create three layer on new pdf using iTextSharp.
 
Now i want to open this pdf in adobe reader and i want to add comments on these three layer separately as regular pdf commenting option.
 
But problem is, it is not saving on respective layer, it is saving on pdf.
 
On/Off action of pdf layer for comment is not working.
 
can you guide me how to proceed further.
 
Thank You all