Please note that if you open PDF form opens up blank, then you might be using some other PDF viewer and not Reader.
If Apple Mail Preview, Safari or iBooks opens a fillable form, then it will not display the filled data.
You might need to tap and hold the attachment which will open a selection window. Choose Adobe Reader icon and then open the file with all the filled data visible.
Hope that helps.
[topic moved to Reader/Acrobat DC for Mobile forum]