Apache PDFBox - The Apache PDFBox™ library is an open source Java tool for working with PDF documents.
Saint Paint Studio - Saint Paint - The Essential Image Editor
iTextPDF - iText offers flexible tools for PDF creation, editing and inspection.
Stet.io - Stet.io is a high-quality pixel management platform that allows editing the pictures with online commands or multiple options with real-time effects or filters.
IronPDF - SDK for creating and editing PDFs.
ImageForge - - ImageForge Standard Freeware Edition: