SumatraPDF是一款小型开源的pdf阅读工具。虽然玲珑小巧（只有800多KB），但基本功能一样不差。可以放在U盘中，随时随地阅读。-SumatraPDF is a small open-source tool for pdf reading. Although Linglong compact (only more than 800 KB), but the basic function of the same not bad at all. Can be put on the U sit