2. How to keep your cad signature from being copied: The way to BUG is to make something you don't want to copy into an unknown block. It cannot be copied or modified. This method is highly recommended. After all, using bugs will definitely not be put into use in the new version, and it will also cause some other problems.
3. Actually, CAD has the function of publishing your DWG file into DWF file. While maintaining the vector format, it is not allowed to modify, and of course it cannot be copied.
4. It may be copied from someone else's layout, and a format is set to protect the signature.