A permanent license is a license that does not expire. It continues to authorize access to PDF Reader Mac (or Windows) indefinitely, but users with the license can only access the offline converter (Solution: Standard). You can additionally purchase "Kdan Credit" that gives you access to convert files and send faxes online.
Document 365 Subscription Plan
The Document 365 Subscription plan gives you access to all pro features and services you need across PDF Reader mobile and desktop apps. The plan includes monthly, quarterly, and yearly plans. You will be charged based on the subscription period of the plan you choose, and subscriptions will renew automatically, on your renewal date, until you cancel.
With Document 365 subscription, it gives you uninterrupted access to new versions and releases of PDF Reader all versions along with priority customer support.