PDFKit is a popular JavaScript library that allows developers to create and manipulate PDF documents directly in web applications. It provides a simple API for generating PDFs, making it easy to add text, images, and shapes. This flexibility enables users to create customized documents for various purposes, such as reports, invoices, and forms. The library is built on top of Node.js, which means it can be used in both server-side and client-side applications. With PDFKit, developers can streamline the process of generating PDFs, enhancing user experience and saving time in document creation.