A strong and fast dwg tools, Protecting drawing file, Keep others from modifying/copying your design. DWGLock is a stand-alone application, no AutoCAD required; Supports AutoCAD R2.9 thru 2009 drawings.
Features:
Powerful encryption abilities, secure Maximize security for the entities in the drawing, they can not copy nor change it.Say No to any arbitrary use of your designs;
Recipients can open up to view protected drawing without any inconvenience, they can even add lines, markup.Preserve or discard their comments, its all up to you!
The drawing owner can lock or unlock the source drawing with a password;
Batch encrypt/un-encrypt many files or folders just in one go.

The license of this software is Free Trial Software, the price is $330, you can free download and get a free trial before you buy. If you want to get a full or nolimited version of AutoDWG DWGLock, you can buy this cad software software.