What is the Adobe Approved Trust List?

The Adobe Approved Trust List is a program that allows millions of users around the world to create digital signatures that are trusted whenever the signed document is opened in Adobe® Acrobat® or Reader® software. Essentially, both Acrobat and Reader have been programmed to reach out to a web page to periodically download a list of trusted "root" digital certificates. Any digital signature created with a credential that can trace a relationship ("chain") back to the high-assurance, trustworthy certificates on this list is trusted by Acrobat and Reader.

How to update the Adobe Approved Trust List

From within Adobe Reader go to Edit > Preferences and scroll down to Trust Manager.

Under Automatic Adobe Approved Trust List (AATL) updates, press Update Now and ensure to tick the Load trusted certificates option: