ViewCompanion Pro - description from Softdepia.com:
ViewCompanion? is a powerful application for viewing and printing HPGL and HPGL/2 files generated by your CAD program or plotter driver. The HP-RTL format is also supported, so HPGL/2 files with embedded pictures will be shown correctly. ViewCompanion can convert the viewed file to many other standard formats.
The following formats are currently supported:
CALS Group 4 Raster
Computer Graphics Metafile (CGM)
Paintbrush PCX (PCX)
Portable Network Graphics (PNG)
Windows Bitmap (BMP)
Windows Enhanced Metafile (EMF)
Windows Metafile (WMF)
Both Autodesk Drawing Web Format (DWF) and Adobe PDF are very useful and popular formats for distributing drawings on the Internet. You can use ViewCompanion to convert any HPGL file back to AutoDesk DXF format which you can read in any major CAD application, eg: Autodesk AutoCAD.
ViewCompanion gives you advanced functions for zooming and panning, so that you can view your plot files fast and accurate, before actually plotting them. The program also supports Microsoft's new IntelliMouse for zooming and panning operations.
The Pro version also allows you to add markups to the loaded file. Among the supported markup elements you will find rectangles, ellipses, polygons, text, arrows and images.
Batch printing and conversion functionality is integrated into the program.
ViewCompanion Pro is a "Free to try" program. You can download and try it for an evaluation period.