HotDocs - Template-driven, automated document & form assembly software
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
docassemble - docassemble is a free, open-source expert system for guided interviews and document assembly.
PdfPig - Read and extract text and other content from PDFs in C# (port of PDFBox)
Docsmore - Docsmore is a cloud-based solution that helps organizations with data driven and smart docs. #workflow #esign #documentgeneration #digitaltransformation
Document .Net - Gives you API to do everything with a document in PDF, DOCX, DOC, RTF, HTML and Text formats.