FAQ: Why Do I Get The "File may be read-only or in use." Message When Digitally Signing an AutoLISP File?

The "File may be read-only or in use." error message is displayed when a digital signature can't be attached to a file with the Attach Digital Signatures (AcSignApply.exe) tool.

Some of the reasons for the error message being displayed are:

• The file is open or locked in memory by an application or the operating system.
• The file is located on a drive that you don't have write access.
• The digital certificate you selected might be corrupt.