iTextSharp

iTextSharp is a library that allows you to generate PDF files on the fly. iTextSharp is a port of the iText, a free Java-Pdf library.

http://itextsharp.sourceforge.net/

PDF Clown

PDF Clown is a Java/.NET library for manipulating PDF files, with multiple abstraction layers to satisfy different programming styles: from the lower level (PDF object model) to the higher (PDF document structure and content streaming).

http://clown.stefanochizzolini.it/

PDFjet - Open Source Edition

A library for dynamic generation of PDF documents from Java and .NET.
Create PDF documents and reports with just a few lines of Java or C# code.

http://pdfjet.com/index.html

Report.NET

Report.NET is a powerful library that will help you to generate PDF documents in a simple and flexible manner. The document can be created with data that have been retrieved from any ADO.NET data set. The Report.NET library is available for free under the LGPL license.

Features
- entirely written in C# for the Microsoft .NET framework
- very compact code (Hello World: 6 lines)
- supported graphic objects: text, lines, rectangles, jpeg images
- easy alignment and transformation of graphic objects
- ASP.NET can generate dynamic PDF pages
- XML Documentation (Comment Web Pages)

http://report.sourceforge.net/

PDFsharp

PDFsharp is the Open Source library that easily creates PDF documents from any .NET language.The same drawing routines can be used to create PDF documents, draw on the screen, or send output to any printer.

http://www.pdfsharp.com/

SharpPDF

SharpPDF is a C# library that implements different objects for the creation of PDF documents with few steps. It is created for .NET framework 1.1 and it can create 100% compatible PDF (tested with Acrobat Reader, Ghostscript , JAWS PDF Editor and other PDF readers). The most important goal of this library is the simple way of use.
It can be used in many ways:

• You can use it with Windows Forms to generate new pdf files or to save them on a database.
• You can use it with Web Applications (ASP.NET) to generate files or to get them directly into the browser.

http://sharppdf.sourceforge.net/

ASP.NET FO PDF

FO PDF is similar to ASP.NET Server Controls, written in C#.It takes DataTable and few other params to generate the XSL FO and renders a DataGrid like PDF Report using NFOP (Apache FOP Port in J#) PDF Formatter.More tags to generate XSL FO will be added.

http://sourceforge.net/projects/npdf/

NFop

NFop is a Formatting Objects Processor (FOP) for XSL-FO that runs on the .NET Framework. It is a port from the Apache XML Project's FOP Java source to .NET's Visual J#. This makes it great for pure .NET reporting modules.

http://sourceforge.net/projects/nfop/