How to split 1 large MS Word file into multiple files

To run a macro, click the button on the Quick Access Toolbar, press the keyboard shortcut, or you can run the macro from the Macros list.
Click View > Macros > View Macros.

In the list under Macro name, click the macro you want to run.
Click Run.

The second- my code for introduce you:
Method 1
Sub SlpipFile()
Dim i As Long
Application.ScreenUpdating = False
ChangeFileOpenDirectory ActiveDocument.Path
Selection.Find.ClearFormatting
With Selection.Find
.Text = “^k”
.Forward = True
.Wrap = wdFindContinue
End With
ActiveDocument.Range(0, 0).Select
Do Until Selection.Find.Execute = False
i = i + 1
Selection.MoveRight Unit:=wdCharacter, Count:=1
Selection.MoveDown Unit:=wdParagraph, Count:=999999999, Extend:=wdExtend
Selection.Cut
Selection.TypeBackspace
ActiveDocument.SaveAs “File_” & VBA.Format(i, “000”) & “.doc”, 0
ActiveDocument.Close
Documents.Add DocumentType:=wdNewBlankDocument
Selection.Paste
ActiveDocument.Range(0, 0).Select
Loop
ActiveDocument.SaveAs “File_” & VBA.Format(i + 1, “000”) & “.doc”, 0
Application.ScreenUpdating = True
End Sub

Method 2:
Option Explicit
Sub SlpipFile3()
Dim i As Long
Dim tennv
Dim Fname
Application.ScreenUpdating = False
ChangeFileOpenDirectory ActiveDocument.Path
‘Selection.Find.ClearFormatting
With Selection.Find
.Text = “^k”
.Forward = True
.Wrap = wdFindContinue
End With
ActiveDocument.Range(0, 0).Select
Do Until Selection.Find.Execute = False
i = i + 1
Selection.MoveRight Unit:=wdCharacter, Count:=1
Selection.MoveDown Unit:=wdParagraph, Count:=999999999, Extend:=wdExtend
Selection.Cut
Selection.TypeBackspace
Selection.HomeKey Unit:=wdStory
Selection.GoTo What:=wdGoToLine, Which:=wdGoToNext, Count:=1, Name:=””
Selection.GoTo What:=wdGoToLine, Which:=wdGoToNext, Count:=1, Name:=””
Selection.EndKey Unit:=wdLine, Extend:=wdExtend
Selection.MoveLeft Unit:=wdCharacter, Count:=1, Extend:=wdExtend
tennv = Mid(Selection.Text, InStr(1, Selection.Text, “: “) + 1, Len(Selection.Text))
Fname = “File_” & tennv & “.docx”
ActiveDocument.SaveAs2 FileName:=Fname, FileFormat:=wdFormatXMLDocument, LockComments:=False, _
Password:=””, AddToRecentFiles:=True, WritePassword:=””, _
ReadOnlyRecommended:=False, EmbedTrueTypeFonts:=False, _
SaveNativePictureFormat:=False, SaveFormsData:=False, SaveAsAOCELetter:= _
False, CompatibilityMode:=14
Documents.Add DocumentType:=wdNewBlankDocument
Selection.PasteAndFormat (wdUseDestinationStylesRecovery)
ActiveDocument.Range(0, 0).Select
Loop
Application.Quit
Application.ScreenUpdating = True
End Sub

MEthod 3Option Explicit

Sub SplitFile()
Dim i As Long
Dim Stt As String
Dim Fname As String

Application.ScreenUpdating = False
ChangeFileOpenDirectory ActiveDocument.Path

Selection.HomeKey Unit:=wdStory
Selection.Find.ClearFormatting

With Selection.Find
    .Text = “B?NG CHI TI?T TÍNH THU? TNCN NÃM”
    .Forward = True
    .Wrap = wdFindContinue
    .MatchWildcards = True
    .Execute
End With
Selection.MoveDown Unit:=wdLine, Count:=1
‘ActiveDocument.Range(0, 0).Select
Do Until Selection.Find.Execute = False
    i = i + 1
‘    Selection.Delete Unit:=wdCharacter, Count:=1
    Selection.HomeKey Unit:=wdLine
    Selection.EndKey Unit:=wdStory, Extend:=wdExtend
    Selection.Cut
 
    Selection.HomeKey Unit:=wdStory
    Selection.Find.ClearFormatting
    With Selection.Find
        .Text = “K? và ghi r? h? tên”
        .Forward = True
        .MatchWildcards = True
        .Execute
    End With
    Selection.MoveRight Unit:=wdCharacter, Count:=1
    Selection.EndKey Unit:=wdStory, Extend:=wdExtend
    Selection.Delete Unit:=wdCharacter, Count:=2

    Selection.HomeKey Unit:=wdStory
    Selection.Find.ClearFormatting
    With Selection.Find
        .Text = “STT*: “
        .Replacement.Text = “”
        .Forward = True
        .Wrap = wdFindContinue
        .MatchWildcards = True
        .Execute
    End With
    Selection.MoveRight Unit:=wdCharacter, Count:=1
    Selection.EndKey Unit:=wdLine, Extend:=wdExtend
    Selection.MoveLeft Unit:=wdCharacter, Count:=1, Extend:=wdExtend
    Stt = Selection.Text
    Selection.Find.ClearFormatting
    With Selection.Find
        .Text = “Tên nhân viên*: “
        .Forward = True
        .Wrap = wdFindContinue
        .MatchWildcards = True
        .Execute
    End With
    Selection.MoveRight Unit:=wdCharacter, Count:=1
    Selection.EndKey Unit:=wdLine, Extend:=wdExtend
    Selection.MoveLeft Unit:=wdCharacter, Count:=1, Extend:=wdExtend
    Fname = “File_” & Stt & “_” & Selection.Text & “.docx”
    ActiveDocument.SaveAs2 FileName:=Fname, FileFormat:=wdFormatXMLDocument, LockComments:=False, _
         Password:=””, AddToRecentFiles:=True, WritePassword:=””, _
        ReadOnlyRecommended:=False, EmbedTrueTypeFonts:=False, _
        SaveNativePictureFormat:=False, SaveFormsData:=False, SaveAsAOCELetter:= _
        False, CompatibilityMode:=14
 
    Selection.WholeStory
    Selection.Paste
    Selection.HomeKey Unit:=wdStory
    Selection.MoveDown Unit:=wdLine, Count:=1
    Selection.Find.ClearFormatting
    With Selection.Find
        .Text = “B?NG CHI TI?T TÍNH THU? TNCN NÃM”
        .Forward = True
        .Wrap = wdFindContinue
        .MatchWildcards = True
        .Execute
    End With
Loop

    Selection.Find.ClearFormatting
    With Selection.Find
        .Text = “STT*: “
        .Forward = True
        .Wrap = wdFindContinue
        .MatchWildcards = True
        .Execute
    End With
    Selection.MoveRight Unit:=wdCharacter, Count:=1
    Selection.EndKey Unit:=wdLine, Extend:=wdExtend
    Selection.MoveLeft Unit:=wdCharacter, Count:=1, Extend:=wdExtend
    Stt = Selection.Text
    Selection.Find.ClearFormatting
    With Selection.Find
        .Text = “Tên nhân viên*: “
        .Forward = True
        .Wrap = wdFindContinue
        .MatchWildcards = True
        .Execute
    End With
    Selection.MoveRight Unit:=wdCharacter, Count:=1
    Selection.EndKey Unit:=wdLine, Extend:=wdExtend
    Selection.MoveLeft Unit:=wdCharacter, Count:=1, Extend:=wdExtend
    Fname = “File_” & Stt & “_” & Selection.Text & “.docx”
    ActiveDocument.SaveAs2 FileName:=Fname, FileFormat:=wdFormatXMLDocument, LockComments:=False, _
         Password:=””, AddToRecentFiles:=True, WritePassword:=””, _
        ReadOnlyRecommended:=False, EmbedTrueTypeFonts:=False, _
        SaveNativePictureFormat:=False, SaveFormsData:=False, SaveAsAOCELetter:= _
        False, CompatibilityMode:=14
MsgBox “done!” & Chr(13) & “There’s ” & i + 1 & ” page(s) were saved !”
Application.ScreenUpdating = True
End Sub

Test file:download here
comment for my helping