Try:
Sub Test()
Dim curTypemark As String
Dim oPar As Paragraph ' placeholder for a paragraph
Dim oRng As Range
curTypemark = vbNullString
With ActiveDocument
.Paragraphs.LineSpacingRule = wdLineSpaceDouble
.Content.Font.Size = 12
.Content.Font.Name = "Times New Roman"
For Each oPar In .Paragraphs
Set oRng = oPar.Range
oRng.Select
If Not oRng.Information(wdWithInTable) Then
If (oPar.Style = "tx" Or oPar.Style = "sb1tx") Then
oRng.MoveEnd Unit:=wdCharacter, Count:=-1
oRng.InsertAfter (vbCr)
End If
If (Not (curTypemark = oPar.Style)) Then
curTypemark = oPar.Style
oRng.InsertBefore ("<" + curTypemark + ">")
If (Not (oPar.Style = "cn" Or oPar.Style = "tx" Or oPar.Style = "ins-art" Or oPar.Style = "ins-photo" Or oPar.Style = "a" Or oPar.Style = "b" Or oPar.Style = "c" Or oPar.Style = "d")) Then
oRng.MoveEnd Unit:=wdCharacter, Count:=-1
oRng.InsertAfter (vbCr)
End If
If (oPar.Style = "a" Or oPar.Style = "b" Or oPar.Style = "c" Or oPar.Style = "d") Then
oRng.MoveEnd Unit:=wdCharacter, Count:=-1
oRng.InsertBefore (vbCr)
End If
End If
End If
Next
End With
End Sub