P.S. Looks like this same question was asked by someone else in 2012 here:
Re: Looks like "COPY" has been stamped on all pages of PDF file.
He was told to e-mail adobereader-android@adobe.com and that is what I did to start with as well, since that's listed as the support address if you look at the details of the app on the tablet. However, that bounced back with a failure message, but additionally sent me an auto reply message, and it said to post here instead of e-mailing.
That question from 2012 is still not marked as answered.