From Software Companions:
ViewCompanion Standard is an application for viewing and printing files generated by your CAD program or plotter driver. Since the HP-RTL format is supported, your HPGL/2 files with embedded images will be shown correctly. It allows you to add markups to the loaded file. Among the supported markup elements you will find rectangles, ellipses, polygons, text, arrows, stamps and images. Markup elements will be stored in a separate file and the original file will not be changed.