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
Adobe Reader - Adobe Acrobat Reader is a free tool for viewing documents that have been stored in Adobe's Portable Document Format (PDF).
PdfPig - Read and extract text and other content from PDFs in C# (port of PDFBox)
Adobe Acrobat DC - Make your job easier with Adobe Acrobat DC, the trusted PDF creator. Use Acrobat to convert, edit and sign PDF files at your desk or on the go.
PDFSharp - Office & Productivity and Development
CutePDF - CutePDF is a simple but entirely powerful PDF files creator, converter, and virtual printer.