Sumatra PDF is a free and open-source document viewer that supports many document formats including: Portable Document Format (PDF), Microsoft Compiled HTML Help (CHM), DjVu, EPUB, FictionBook (FB2), MOBI, PRC, Open XML Paper Specification (OpenXPS, OXPS, XPS), and Comic Book Archive file (CB7, CBR, CBT, CBZ).

"[11][12][13] Other open-source readers like Okular and Evince make this optional, and Debian patches software to remove these restrictions, in accord with its principles of interoperability and re-use.

[17] Sumatra supports SyncTeX, a bidirectional method to synchronize TeX source and PDF output produced by pdfTeX or XeTeX.

[19] Initially, Kowalczyk did not release a 64-bit version of Sumatra, indicating that while it might offer slightly more speed and available memory, he believed at that time that it would greatly add to user confusion and that the benefits would not outweigh the potential costs.

Due to US export legal restrictions, it was unavailable "in countries on the United States Office of Foreign Assets Control sanction list, including Cuba, Iran, North Korea, Sudan and Syria.

Poppler remained as alternative engine for a time, and from version 0.6 to 0.8 it was automatically used to render pages that MuPDF failed to load.

[10] In 2007, the first unofficial translations were released by Lars Wohlfahrt[28] before Sumatra PDF got official multi-language support.

[31] Sumatra has attracted acclaim for its speed and simplicity,[32] for being portable,[33] its keyboard shortcuts, and its open-source development.

As foundation representative Heiki Ojasild explained, "while they continue to make use of the non-free library, SumatraPDF cannot be recognised as Free Software.