A PDF SDK (Software Development Kit) is a set of tools and libraries that developers use to create, manipulate, and manage PDF documents within their applications. It provides functionalities such as viewing, editing, and converting PDF files, allowing developers to integrate PDF capabilities seamlessly into their software. Using a PDF SDK can save time and effort, as it offers pre-built functions and features that would otherwise require extensive coding. This enables developers to focus on their application's core functionality while ensuring robust handling of PDF documents, enhancing user experience and productivity.