SolidWorks is the only program that makes eDrawing files (.edrw, .easm) out of many CAD drawings or 3D models (such as .igs).
Other programs like AutoCAD, CATIA, Inventor and perhaps other need a special eDrawings Publisher plugin that allows them to export their CAD data to EDRW format.
eDrawings are like some sort of PDF format for CAD. Only meant for viewing and sharing, but not for editing. A special eDrawings viewer is used for opening the files, it can be download for free from SolidWorks website.