PDF libraries are software tools that allow developers to create, manipulate, and manage PDF documents programmatically. These libraries provide functions for tasks such as generating new PDFs, editing existing ones, extracting text, and adding images or annotations. They are commonly used in applications that require document handling, such as report generation and form processing. Many programming languages have their own PDF libraries, such as iText for Java, PyPDF2 for Python, and PDF.js for JavaScript. These libraries simplify the process of working with PDFs, making it easier for developers to integrate PDF functionalities into their applications without needing to understand the complex PDF file format.