PdfPig - Read and extract text and other content from PDFs in C# (port of PDFBox)
Kdan PDF Reader - The All-in-One Document Expert Designed for the Increasingly-mobile Workplace.
Document .Net - Gives you API to do everything with a document in PDF, DOCX, DOC, RTF, HTML and Text formats.
Qoppa Software - Qoppa Software offers a suite of products that cover every aspect of PDF processes and integrate seamlessly into document workflows.
PDFSharp - Office & Productivity and Development
PDFJet - PDFJet is a mobile and cloud PDF Library for Java and .NET to generate PDF documents.