To be able to share with Word 2010 users perhaps you could do something like this:
Sub Document_Open()
Dim bCompatible As Boolean
On Error Resume Next
bCompatible = ActiveDocument.Variables("Compatible")
If Err.Number <> 0 Then
ActiveDocument.Variables("Compatible") = "False"
bCompatible = False
End If
On Error GoTo 0
If Application.Version < 15# And ActiveDocument.Variables("Compatible") = "False" Then
If MsgBox("This document was created in Word 2013 or higher and contains mapped rich text content controls." & vbCr + vbCr _
& "To view this document in Word 2010 or lower it must be saved as a ..." & vbCr + vbCr _
& "Do you want to ...", vbQuestion + vbYesNo, "COMPATIBILITY") = vbYes Then
Dialogs(wdDialogFileSaveAs).Show
ActiveDocument.Variables("Compatible") = "True"
Else
ActiveDocument.Close ""
End If
End If
End Sub