Would you please let us know if you are using the desktop version of Acrobat/Reader DC on a Windows or Mac computer?
You posted your question to the mobile forum. We can move it to the Acrobat Reader (desktop app) forum or the Editing & Exporting PDFs (for Acrobat Pro/Standard desktop app) forum, if you are using the desktop app.
I seem to be having the same problem. I just subscribed for 1year to Acrobat DC Pro so that I could edit pdf's on my iPad, but so far, I have been unable to edit my pdf's as I can easily do that on my desktop. That was one of the advertised features of subscribing, i.e. being able to edit on my iPad. I hope someone can chime in with an answer ✌