SumatraPDF is a free and lightweight PDF reader designed for Windows. It allows users to open and view PDF files quickly without consuming too many system resources. The interface is simple and user-friendly, making it easy for anyone to navigate through documents. In addition to PDFs, SumatraPDF supports various file formats, including ePub, MOBI, and XPS. This versatility makes it a handy tool for reading different types of digital content. With its focus on speed and efficiency, SumatraPDF is a great choice for those who need a reliable and straightforward document viewer.