how to update hyperlink text in pdf using itextsharp in c#

0 down vote favorite my requirement is need to update hyperlink and hyperlink text in pdf using Itextsharp in c#.net application.I can able to update hyperlink address but how to change hyperlink text for example : hyperlink is : http://www.google.com hyperlink text is : ClickHere I want change "ClickHere" to "SearchHere" Any help,Appreciated