If you are looking for free, easy, and accurate ways to view an AutoCAD DWG here are two great options using native DWG technology from Autodesk.
First a desktop DWG Viewer – DWG TrueView
There is the Windows based desktop application named DWG TrueView which can not only view 2D and 3D DWG files but even includes layer features, visual styles, measurement, and print/plot feature of the full AutoCAD. You can view not only the DWG files created with AutoCAD 2012 but read DWG files from the early 1980’s from AutoCAD 2.x and even batch convert DWG files to different several versions. You can also create DWF and PDF documents.
It is a hefty 270Mb download but it is very powerful and free.
Desktop DWG Viewing:
Autodesk DWG TrueView http://www.autodesk.com/trueview
A web and mobile DWG Viewer – AutoCAD WS and AutoCAD WS Mobile
AutoCAD WS is a web and mobile based DWG viewer with markup and collaboration. The beauty of this application is not only does it run on any desktop with a browser supporting Flash, it is also available as a mobile application on Apple and Android devices. AutoCAD WS requires only a Internet browser such as Safari, Internet Explorer, Chrome, or Firefox with Flash installed. AutoCAD WS mobile supports offline file synch so you can take you drawings even where you do not have any web connection. Imagine all your construction drawings on your mobile device to check a job site and make some as-built mark ups. Currently AutoCAD WS supports 2D DWG and real-time collaboration, AutoCAD integration, and unlimited file storage. In addition to being able to upload, edit, markup, and share in real-time with DWG files you can also upload other file types like ZIP, Doc, and PDF files as a file storage solution.
As fast as the AutoCAD WS team has been in adding more features at the request of the hundreds of thousands of users I am sure there will be a ton of new exciting things for AutoCAD WS users in the works.
Web and Mobile DWG Viewing
AutoCAD WS http://www.autocadws.com/
Web and Mobile DWF Viewing
If you are using the much smaller DWF (Design Web Format), there is the free desktop application Autodesk Design Review and Freewheel and now the new Autodesk Labs Technology Preview Project Nitrous.
Cheers,
Shaan