From: http://support.microsoft.com/?kbid=306348

Microsoft Knowledge Base Article - 306348    
How to Programmatically Save Each Page or Section of a Document As Separate File 
The VBA macro for Word "BreakOnSection()"


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Sub BreakOnSection()
   ' Used to set criteria for moving through the document by section.
   Application.Browser.Target = wdBrowseSection

   'A mailmerge document ends with a section break next page.
   'Subtracting one from the section count stops error message.
   For i = 1 To ((ActiveDocument.Sections.Count) - 1)
   
      'Select and copy the section text to the clipboard
      ActiveDocument.Bookmarks("\Section").Range.Copy

      'Create a new document to paste text from clipboard.
      Documents.Add
      Selection.Paste

   ' Removes the break that is copied at the end of the section, if any.
      Selection.MoveUp Unit:=wdLine, Count:=1, Extend:=wdExtend
      Selection.Delete Unit:=wdCharacter, Count:=1

     ChangeFileOpenDirectory "C:\"
      DocNum = DocNum + 1
     ActiveDocument.SaveAs FileName:="test_" & DocNum & ".txt", FileFormat:=wdFormatDOSTextLineBreaks
     ActiveDocument.Close
      ' Move the selection to the next section in the document
     Application.Browser.Next
   Next i
   ActiveDocument.Close savechanges:=wdDoNotSaveChanges
End Sub
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In the Knowledge Base Article, the line to save each section as a separate file reads

     ActiveDocument.SaveAs FileName:="test_" & DocNum & ".doc"

which saves files as test_1.doc, test_2.doc, etc., in Word's usual .doc format, including
a lot of extra information needed for word processing.  Changing that line as here, to read 

     ActiveDocument.SaveAs FileName:="test_" & DocNum & ".txt", FileFormat:=wdFormatDOSTextLineBreaks

instead saves each file with a suffix ".txt" and in a simple text format needed
for an HTML page.  Further changes to that line could save the files in filenames
derived from a field in the document, which can save a bit of work renaming files.