Sub OpenFiles()

Dim l As Long ' left most position
Dim h As Long ' height of window
Dim w As Long ' width of window
Dim p As String 'file path
Dim f1 As String, f2 As String, f3 As String 'file names

p = "E:\" '<----- your file path
f1 = "One.docx" '<----- your left most file
f2 = "Two.docx" '<----- your next left most file
f3 = "Three.docx" '<----- your next left most file

l = 0 '<----- window starting point
w = 250 '<----- your window width
h = 800 '<----- your window height

'File 1
Documents.Open p & f1

With Tasks(f1)
    .WindowState = wdWindowStateNormal
    .Move Top:=0, Left:=l
    .Width = w
    .Height = h
End With

'File 2
Documents.Open p & f2

With Tasks(f2)
    .WindowState = wdWindowStateNormal
    .Move Top:=0, Left:=l + w
    .Width = w
    .Height = h
End With

'File 3
Documents.Open p & f3

With Tasks(f3)
    .WindowState = wdWindowStateNormal
    .Move Top:=0, Left:=l + w + w
    .Width = w
    .Height = h
End With

End Sub