This is done through the cross-reference feature (or References > Cross-Reference).
Do your numbering following the instructions at
How to create numbered headings or outline numbering in Ribbon Versions of Word by Shauna Kelly.
Will the cross-references update automatically?
Yes, and no.
These are fields. They will update when fields update. They generally update upon printing. You can force an update on a field by selecting it and pressing the F9 function key. You can update all fields by pressing Ctrl+A followed by the F9 key.
The cross-reference is also a hyperlink (not formatted to look like one, but it acts like one). The hyperlink updates automatically.
Complex Documents
The following macro would update all of the REF fields in a document:
Code:
Sub UpdateAllRef()
' Based on code at http://www.gmayor.com/installing_macro.htm
' Update all Ref fields in a document, even if in headers/footers
Dim oStory As Range
Dim oField As Field
'
For Each oStory In ActiveDocument.StoryRanges
For Each oField In oStory.Fields
If oField.Type = wdFieldRef Then oField.Update
Next oField
'
If oStory.StoryType <> wdMainTextStory Then
While Not (oStory.NextStoryRange Is Nothing)
Set oStory = oStory.NextStoryRange
For Each oField In oStory.Fields
If oField.Type = wdFieldRef Then oField.Update
Next oField
Wend
End If
'
Next oStory
'
Set oStory = Nothing
Set oField = Nothing
End Sub
For instructions on using a macro, see
Installing Macros.