Used AutoDWG DWGLock for Windows?
Developer’s Description
By AutoDWG
A 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. Powerful encryption, secure the entities in the drawing, they can not copy nor change it. Recipients can open up protected drawing, and add lines etc to the drawing file.
Explore More

Sponsored
Adobe Stock
Trial versionRotation Pilot
Trial versionImage Converter Free
Free
PhotoPerfect DigiCam
Trial versionCapture
Trial version
FreeSizer Portable
Free
OldMovie
Trial version
Urban Painter
Free
Photoshop Manga Effect Plugin (64-bit)
Trial version
DWF to DWG Converter Pro
Trial versionPng2Ico
Trial version
Bluebeam Vu
Free