Copied from AUGI Link
There are all sorts of new, fancy ways to share your Civil files and documentation internally and with clients. Let’s not forget, however, the many ways available to us over the years. The first of these methods I’d like to explore is through working with the PROXYGRAPHICS system variable.
Although not a complete solution, understanding how the PROXYGRAPHICS setting works will be your first round of defense for sharing intelligent AutoCAD® Civil 3D® files with your coworkers, subcontractors, or clients not utilizing Civil 3D for their own efforts. Proxy graphics store the last viewed image of Civil 3D objects, which lets users view your drawing without modifying the original objects. Also, they only hold the graphical representation of the current, active viewport when the drawing file is saved.
Setting up the PROXYGRAPHICS system variable is easy enough. Simply type it in at the command line and set it to “1.” The default is “0” and we’ll explore the differences in this section as a point of comparison. With PROXYGRAPHICS set properly, SAVE your drawing.
Figure 1: A drawing file created with Civil 3D, saved with PROXYGRAPHICS set to “0” and opened in AutoCAD®. Note the Civil 3D entities are broken. (Compare with Figure 2.)
Figure 2: A drawing file created with Civil 3D and saved with PROXYGRAPHICS set to “1” and opened in AutoCAD.
It isn’t that simple, though, as there is an immediately apparent downfall of using PROXYGRAPHICS to control the visibility for your Civil 3D entities. The more complex a drawing file, the larger it becomes with PROXYGRAPHICS set to “1” compared with the default. Such a problem this may become, Autodesk even suggests in the Help documentation to save a copy of the original before attempting to apply the PROXYGRAPHICS system variable to your drawings.
Figure 3: The PROXYGRAPHICS system variable has a drastic effect on file size.
The better option when going for a low-tech option for sharing your files? See if you can convince your counterpart or client to download and install the Civil 3D object enablers for their AutoCAD installation (http://usa.autodesk.com/support). It will save everyone time and headaches in the long run. However, proxy graphics are your only option for sharing on AutoCAD WS.