Or you could use a bit of VBA to open each document and change the
Author. First place all of the files in a common directory. In this
example is used:

C:\Batch Folder

Public Sub BatchChangeProperty()

Dim myFile As String
Dim PathToUse As String
Dim myDoc As Document

PathToUse = "C:\Batch Folder\"
'Close all open documents before beginning
On Error Resume Next
Documents.Close SaveChanges:=wdPromptToSaveChanges
On Error GoTo 0
'Set the directory and type of file to batch process
myFile = Dir$(PathToUse & "*.doc")
While myFile ""
'Open document
Set myDoc = Documents.Open(PathToUse & myFile)
'Make the change
ActiveDocument.BuiltInDocumentProperties("Author") .Value = "Your new
name"
'Close the modified document after saving changes
myDoc.Close SaveChanges:=wdSaveChanges
'Next file in folder
myFile = Dir$()
Wend
End Sub