You see, if you want to avoid 3-rd party libraries, you maybe bound to creation of your own. Could you afford it? However, if you want to use only 3rd-part source code but not precompiled executables, this is very reasonable. I would recommend to use iTextSharp. This is a .NET port of iTextSharp, an Open Source library used to work with PDF.
] (you can download iTextSharp here).