Kdan PDF Reader - The All-in-One Document Expert Designed for the Increasingly-mobile Workplace.
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
Qoppa Software - Qoppa Software offers a suite of products that cover every aspect of PDF processes and integrate seamlessly into document workflows.
PdfPig - Read and extract text and other content from PDFs in C# (port of PDFBox)
RadaeePDF - RadaeePDF is a library for developers who want to render, manipulate, annotate PDF files on Android, iOS and Windows.
PDFSharp - Office & Productivity and Development