Sumatra PDF is a PDF, ePub, MOBI, CHM, XPS, DjVu, CBZ, CBR reader for Windows

Sumatra PDF vs. Sumatra PDF Reader

Maybe this is a stupid question, but is there a difference between Sumatra PDF and Sumatra PDF Reader?

Depends on if its from another source. the norm is to reference as SumatraPDF [Reader | Viewer] or Sumatra PDF [Reader | Viewer] that is the word reader is optional and can be replaced equally by viewer, see the homepage has headline “Sumatra PDF Viewer” Free PDF Reader - Sumatra PDF but the github source is headed “SumatraPDF Reader”