Please refer the below links.

1. Retrieve and display PDF Files from database in browser in ASP.Net
2. iTextSharp: Add Page numbers to existing PDF using C# and VB.Net

3. How to read pdf file and extract contents using iTextSharp in ASP.Net and C#

4. Read PDF and store its contents in XML file in ASP.Net

i want to know about GroupDocs in asp.net could you please give me any example about groupdocs 

Exactily i want PDf annotation in asp.net please help me

Its better you save the pdf on server and using iTextSharp you can do what ever you want to do as in the above links.

Else refer the below link.

http://stackoverflow.com/questions/85624/component-to-view-and-annotate-pdf-documents

can u give me any sample project using iTextSharp for pdf highlite , marking and underline purpose