GroupDocs
GroupDocs creates easy to use, comprehensive online document management APIs for .NET, Java and Cloud, as well as a range of Cloud apps that improve document collaboration for organizations of any size. GroupDocs saves developers and end users time and money by offering a complete and powerful set of document management APIs allowing users to view, sign, annotate, compare, convert and assemble documents in a wide variety of formats, including Microsoft Word, Excel, PowerPoint and Visio, as well as Adobe Acrobat PDF and many image formats. Flexible workflows and easy-to-use, customizable user interfaces are part of the package.
ComPDFKit
ComPDFKit enable developers to integrate PDF Annotations and Format Conversion, Digital Signature, Smart Forms, OCR, Redaction, and more in to their applications on Windows, macOS, iOS, Android, and the web through their PDF SDKs. Their aim is to offer the most comprehensive library to shorten the project development cycle and to continuously improve their SDK products to meet developer's future requirements as they change and projects evolve.
Jugaad
RadaeePDF SDK is a great PDF rendering and manipulation tool for developers. If you develop mobile or desktop applications the RadaeePDF SDK framework is the "Swiss Army knife" to handle PDF files. More than 6,000 applications are running the SDK on Android, iOS and Microsoft Windows UWP.