Wikipedia
iText is an open source library for creating and manipulating PDF files in Java.
iText was written by Bruno Lowagie, Paulo Soares and others, and as of version 5.0.0 (released Dec 7, 2009) is distributed under the Affero General Public License version 3. Previous versions of iText (Java up to 2.1.7 and C# up to 4.1.6) were distributed under the Mozilla Public License or the LGPL. iText is also available through a proprietary license, distributed by iText Software Corp.
iText provides support for most advanced PDF features such as PKI-based signatures, 40-bit and 128-bit encryption, color correction, Tagged PDF, PDF forms (AcroForms), PDF/X, color management via ICC profiles and barcodes, and is used by several products and services, including Eclipse BIRT, Jasper Reports, Red Hat JBoss Seam, Windward Reports, and pdftk.