用宏来自动处理就可以了。
参考:
Sub AutPar()
Dim m As Integer, n As Integer
On Error Resume Next
m = 1
For n = 1 To ActiveDocument.Characters.Count Step 1999
ActiveDocument.Characters(n).InsertBefore Text:=Chr(13) & "第 " & m & " 章" & Chr(13)
m = m + 1
Next
End Sub