Sumatra PDF is a free PDF, XPS, DjVu, eBook (ePub, Mobi), CBZ and CBR viewer created by Krzysztof Kowalczyk. In comparison to other applications of this type, it is distinguished by its lightness and small size. The program is created with a great emphasis on speed and is addressed to users who, over and above the rich (often unused in everyday work) functionality, translate minimalism and simple solutions.

Sumatra PDF does not pretend to compete with Adobe Reader, but it is perfect for home viewing of documents. The program does not offer tools for marking, colouring, commenting on texts, etc., and its functionality is limited to browsing and searching the content of documents. All this combined with the use of the MuPDF library for rendering makes the application run efficiently, able to be satisfied with small batches of memory.

Despite its many advantages, Sumatra PDF is unfortunately not free of defects. One of the most important is the lack of support for older editions of Windows, which often work on older computers with very limited system resources.