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
ApowerPDF - ApowerPDF is a versatile PDF editor which also features as PDF converter, viewer, creator and more. It provides a perfect solution for all users.
iTextPDF - iText offers flexible tools for PDF creation, editing and inspection.
Icecream Apps PDF Editor - Excellent powerful tool to edit PDF, annotate PDF, redact, protect and more.
Document .Net - Gives you API to do everything with a document in PDF, DOCX, DOC, RTF, HTML and Text formats.
PDF Reader Pro - PDF Reader Pro is an all-in-one PDF office supporting to Read, Annotate, Edit, OCR, Convert, Create & Fill Form, Sign PDFs, TTS on Mac, iOS, Android, and Windows.