Sumatra PDF is a free PDF, eBook (MOBI), XPS, DjVu, CHM, Comic Book (CBZ and CBR) reader for Windows. Sumatra PDF is small and starts up very fast. Simplicity of the user interface has a high priority. Portable version included (a single executable that can be run e.g. from USB drive and doesn't write to registry).
What's new in Sumatra PDF version 3.1.1:
- (re)add support for old processors that don’t have SSE2
- support newer versions of unrar.dll
- allow keeping browser plugin if it’s already installed
- crash fixes