The .NET framework does not contain any native way to work with PDF files. So, if you want to generate or work with PDF files as part of your ASP.NET web application, you will have to rely on one of the many third party components that are available. Google will help you to find one that fits your budget, as well as a range of open-source free components. One of the free components is iTextSharp, which is a port of a well known Java utility, iText.
The main problem with iTextSharp is that it lacks documentation. There are some basic tutorials available, but most programmers have to resort to trying to wrestle with the documentation provided for the Java version - iText - to get going with the component, or you may want to purchase the book iText In Action. However, this only provides guidance in Java. Many of the code samples are transferable to C# without a lot of modification, but if you are relatively new to C#, you may frequently become frustrated with undocumented or inexplicable differences in classes and method names between the two versions. As a final resort, you can always use Reflector to pick the dll apart and examine its innards. So, as part of a series of How To articles, here's how to get started using iTextSharp with code samples in C#. http://www.mikesdotnetting.com/Article/80/Create-PDFs-in-ASP.NET-getting-started-with-iTextSharp