iText
iText is a widely-used open-source Java library for creating and manipulating PDF documents programmatically. It allows developers to generate, edit, and extract content from PDF files, supporting features like text addition, form filling, digital signatures, and document assembly. Originally developed in 2000, it has become a standard tool for PDF processing in Java applications.
Developers should learn iText when building applications that require dynamic PDF generation, such as report generation, invoice creation, or document automation in enterprise systems. It is particularly useful in scenarios where PDFs need to be customized with data from databases or user inputs, and for adding security features like encryption or digital signatures to documents.