Adobe Acrobat Reader Plus vs Premium

I needed to edit a .pdf doc to send to work. Adobe offered me Acrobat Reader Plus through the IOS App Store. This worked for editing and signing the document so I subscribed for one year for twenty dollars. Unfortunately, when I needed to email a document, Adobe asked me to subscribe to Reader Premium. I tried to look up the differences between Reader Plus and Reader Premium, but this was a puzzle in itself. You can't find any reference to Adobe Reader Plus on the Adobe website. Apparently they offer it on the IOS App Store but pretend it doesn't exist otherwise.