iTextPDF - iText offers flexible tools for PDF creation, editing and inspection.
PDF Clown - PDF Clown is an open-source general-purpose library for manipulating PDF documents through multiple abstraction layers, rigorously adhering to PDF 1.7 Specification
PDFSharp - Office & Productivity and Development
ABCpdf.NET - ABCpdf.NET is a high-profile and powerful PDF Library that delivers the best experience possible for everyone.
Document .Net - Gives you API to do everything with a document in PDF, DOCX, DOC, RTF, HTML and Text formats.
wkhtmltopdf - wkhtmltopdf is an open source (LGPL) command line tools to render HTML into PDF and various image...