Our company has an active Enterprise license agreement for Acrobat and other products. One of the key reasons we did this was to enable Federated IDs for access to the applications so that the ID would be integrated to Azure AD. Users that only need Reader and do not require a full-blown licensed copy of Acrobat are not able to login to Reader. The only way to login to Reader is to create a personal, ‘Adobe ID’ which is then outside of corporate control or management. Since Reader is ‘free’ software, there should be no reason that it can’t be added to the list of applications that a Federated ID has the ability to login to.