iTextsharp dll is a free library that helps us specially in creating and manipulating PDF documents. It is a wonderful free ware software for .NET and java to work on PDF documents.In order to use the dll,just browse in google with the name as "itextsharp.dll",you download it onto your machine and add it to bin folder of your respective web application,you are done.The itextsharp .dll contains all the integrated .NET classess in order to create or manipulate on the existing PDF.You can also find the related documentation in the google for itextsharp. dll.