Would you take a look at the following thread?
Another user had exactly the same problem. Please see my reply in the thread and let us know if it works for you.
To prevent the users from renaming files & folders with '.' and unintentionally hiding them, the new version Acrobat DC for iOS now displays an alert dialog.
Hope this helps.
Adding the "." at the beginning of a name is a no-no! It makes the name invisible as you have seen in many operating systems.
I think you have to use an iOS or Android file browser to rename the file, if I recall.
Thanks, that worked!