iText is a free/open source software (F/OSS) project, which lets you read through the full-code API to better assist you in creating a solution.
F/OSS does not mean that it is free of obligations, it just means that the code is freely available.
If you look into the source code of iText, you'll see that most files contain a header referring to the AGPL. You should have received a copy of the GNU Affero General Public License along with this program; if not, visit the GNU license pages.
You must retain the producer line in every PDF that is created or manipulated using iText.
You can be released from the requirements of the license by purchasing a commercial license. Buying such a license is mandatory as soon as you develop commercial activities involving the iText software without disclosing the source code of your own applications. These activities include:
offering paid services to customers as an ASP,
serving PDFs on the fly in a web application,
shipping iText with a closed source product.
The copyright of the iText Software products is owned by Bruno Lowagie and others.
All the core developers of the iText ® project have transferred the Intellectual Property of their work to iText Group NV by signing a Contributor License Agreement.
You can read the full Copyright and Intellectual Property statement here.