iText
iText for Java represents the next level of SDKs for developers
...The iText Suite is a fully-featured SDK for PDF development that allows you to seamlessly embed extensive PDF functionality into your software or workflows. The iText Suite builds on over a decade of lessons learned from iText 5 (and iTextSharp) development. The latest release of iText, version 8, is a simpler, more performant and extensible library that is ready to handle the increased challenges of today's document workflows, one add-on at a time.