SolidWorks technical tips - Edrawings viewer or SolidWorks viewer
eDrawings Viewer or SolidWorks Viewer?
The eDrawings Viewer can open SolidWorks-native parts, assemblies and drawings. So why would you need the SolidWorks Viewer?
eDrawings can open SolidWorks 2001 SP10 documents and later. The SolidWorks Viewer will open all older SolidWorks documents. The Viewer will be needed and supported for some time to come to support legacy data. (Source: Paul Adams, SolidWorks Corp.)