how to store form filled users data in pdf and save on the server

Refer here

http://www.aspsnippets.com/Articles/Export-ASPNet-Web-Page-with-images-to-PDF-using-ITextsharp.aspx

In that case you will have to use some paid tools. ITextSharp is free but it is not so good

http://www.asppdf.com/

There is no inbuilt PDF library in ASP.Net. Hence without any thirdparty tool like ITextsharp.

BTW there's one more that's free

http://www.webresourcesdepot.com/open-source-pdf-library-for-aspnet-pdfsharp/