Portable Document Format (PDF) is a widely used file format for document exchange due to its ability to preserve formatting and security. PDF files are commonly used for sharing documents, reports, and forms across different platforms.

Developers often need to work with PDF files to generate, manipulate, or extract content programmatically. To make this process easier, there are several libraries available that provide tools and functionalities to work with PDF files. In this article, we will discuss 16 of the best free and open-source PDF development libraries.

1. iText: iText is a popular Java library that allows developers to create, modify, and extract content from PDF files. It also supports features like digital signatures, forms, and encryption.

2. PDFBox: Apache PDFBox is an open-source Java library for working with PDF documents. It provides tools for creating, manipulating, and extracting text and images from PDF files.

3. PoDoFo: PoDoFo is a C++ library for reading and writing PDF files. It supports features like text extraction, merging, and encryption.

4. PDF.js: PDF.js is a JavaScript library for rendering PDF documents in web browsers. It allows developers to display PDF files without the need for third-party plugins.

5. PDFtk: PDFtk is a command-line tool for manipulating PDF files. It can be used to merge, split, encrypt, and watermark PDF documents.

6. PDFsharp: PDFsharp is a .NET library for creating PDF documents programmatically. It supports features like text, shapes, images, and forms.

7. Qoppa PDF Library: Qoppa PDF Library is a Java library for working with PDF files. It provides tools for creation, manipulation, and annotation of PDF documents.

8. PDFium: PDFium is an open-source PDF rendering engine developed by Google. It can be used to render PDF files in applications using C++ or JavaScript.

9. PDF.js Express: PDF.js Express is a commercial JavaScript library built on top of PDF.js. It provides additional features like annotations, form editing, and digital signatures.

10. PDF Clown: PDF Clown is a Java library for working with PDF files. It provides tools for reading, writing, and manipulating PDF documents.

11. Apache FOP: Apache FOP is a Java library for formatting and rendering XML documents into PDF files. It supports features like XSL-FO processing and customization.

12. JPedal: JPedal is a Java library for rendering and manipulating PDF files. It provides tools for extracting text, images, and metadata from PDF documents.

13. PDF-LIB: PDF-LIB is a JavaScript library for working with PDF files. It provides tools for creating, modifying, and extracting content from PDF documents.

14. Aspose.PDF: Aspose.PDF is a commercial .NET library for working with PDF files. It supports features like conversion, manipulation, and encryption of PDF documents.

15. PDFsharp-MigraDoc: PDFsharp-MigraDoc is a .NET library for creating PDF documents with text, images, and tables. It provides tools for formatting and layout customization.

16. PDFedit: PDFedit is an open-source PDF editor for Linux. It allows users to manipulate PDF files by adding, deleting, or modifying content.

In conclusion, there are several free and open-source libraries available for developers to work with PDF files. Whether you need to create, modify, or extract content from PDF documents, there is a library that suits your requirements. By using these libraries, developers can streamline their PDF-related tasks and enhance their applications with PDF functionalities.