The Adobe Acrobat Reader for the mobile device is a free application.
You can simply install and use it on your mobile device.
If you have subscribed to any of the subscriptions, you can check it on your Adobe account as JohnSmith mentioned above.
You can also check the same in your application on the device.
Open the application and click on the Home icon at the top left of the screen.
Then at the bottom left, you will see the "My Account" option. Check the screenshot below:
Click on My Account and it will open the account page.
There you will get the option to Sign-In. Once you are signed-in, it will show the list of the subscription available.
At the right of each subscription, it is mentioned either "Subscribed" or "Subscribe".
There you can find if you have purchased any of the subscriptions.
Check and let us know if you have any questions.