Help- editing text in Acrobat Pro

I received a document as a pdf file. I opened it in Acrobat Pro and used the edit text feature.  Once I made the corrections, I resaved the file and emailed it to the client. He sent it back saying the a's, o's, d's, etc. were filled in as black in the box that was edited.  It looks fine on an IMAC, a Mac Book Pro, but on Ipad and Iphone the letters in the edited box are filled in.

Why?

How do I fix this?

Thanks, Mike