One possibility is to use a variation of the following function in conjunction with
http://www.gmayor.com/document_batch_processes.htm which will handle the files and folders.
Make whatever changes to 'oCC' that you require and the add-in will do the same for all matching files in the folder.
Code:
Function Dropdown(oDoc As Document) As Boolean
Dim oCC As ContentControl
On Error GoTo Err_Handler
For Each oCC In oDoc.ContentControls
If oCC.Title = "Dropdown1" Then
With oCC
.Title = "drpVessel"
.Tag = .Title
With .DropdownListEntries
.Clear
.Add "Item 1"
.Add "Item 2"
.Add "Item 3"
.Add "Item 4"
End With
End With
Exit For
End If
Next oCC
Dropdown = True
lbl_Exit:
Exit Function
Err_Handler:
Dropdown = False
Resume lbl_Exit
End Function