i have the key for Acrobat Professional XI, due to my mac OS update the previous version not working so i have removed and installed the Acrobat DC version but it showing for 7 days and how to do activities with the existing key itself.
This is a new product, a major upgrade. You must subscribe to use the new Acrobat DC.
But already we have a subscription, and keys then why need to be new???
I am missing some important info here. You said you had a key for Acrobat XI - but if you have a subscription there is no key. What is the subscription you pay for, as shown in your account details?
its an institution subscription, KAIST.
so institution gave us key to instal on it,
In that case you need to go through your institution's administrator, to find out how to run any upgrade you are entitled to. You cannot download from Adobe's site to get newer product.