That article only mentions signing the accdc package. As far as I am aware, there is no way to usefully sign an accde file.
Of course any file can be signed but that is only useful if the application or operating system can be instructed how to react to the signature. Our network admin once experimented turning a Group Policy that prevented unsigned exe files from running. I signed one myself before he abandoned the policy as more trouble than it was worth.
Similarly I could sign an accde but Access probably wouldn't care if the signature was valid or not, if indeed adding the signature didn't stop it working altogether. Then just running the file would cause it to change and invalidate the signature because it applies to the whole file rather than particular sections as happens with signed Office files.
Signed packages and Trusted Locations look like a Claytons security model to me. My understanding is that the signature on a package just allows it to be extracted into a Trusted Location without a warning.
A user can still copy arbitrary files into a Trusted Location where Office will assume they are fine. Unfortunately users need to have write access to the folder to create the lock file when they run the Access file. Otherwise they will probably, at best, get a read only warning.
Which brings me back to where I started with signatures. My primary goal back in the days of Access 2003 was to avoid the startup warning. I wasn't actually that concerned about security per se.
