if you want pdf document from a link simply use href property of link as address to pdf file. for example you have a label you are showing the pdf file name, write the below code on your dataloading function
lblFile.Text=string.Format("<a href="{0}" target="_blank" title="{1}">{1}</a>",pdffilepath, fileName);
in case of any query plz let me know.
--Pankaj