Hey,
I have reviewed the forums but could not find a solution at all. I have created a few digital IDs to be used in Adobe Acrobat Reader DC, but now, I am unable to remove the ones I saved in Mac Keychain store. From the preferences, I click on "signatures" and then to "identities and trusted certificates" and then to "more". I am able to remove the ones that I saved as files, but not the ones saved as in keychain. I also get warning for the ones that goes "Removing a digital ID is only permitted if the ID was created by Adobe Reader or Acrobat version 8.0 or later."