The official, 100% free viewer built by Autodesk (the creators of the DWG format). It includes accurate measurement tools and built-in DWG version conversion.
If you have purchased a license, activating it is straightforward. According to the official DWGSee purchase resources, the registration process is simple: auto dwgsee pro registration code hot
This is a free, open-source program that lets you view and edit many types of 3D and 2D design files. How to Get AutoDWG See Pro Safely The official, 100% free viewer built by Autodesk