This can be achieved via INCLUDETEXT fields:
1. Create your 4-500 page source document.
2. Bookmark the segments you want to replicate in each of the related documents.
3. Create blank documents for each of the related documents.
4. In a given related document, insert INCLUDETEXT fields pointing to the relevant bookmarks in the source document. To insert the INCLUDETEXT field, choose Insert|Object:Text from File>Range: (type the bookmark name)>Filename: (select the source file)>Insert as Link:Insert
5. Add Tables of Contents, etc. as required, plus any unique text, to each of the related documents.
One benefit of using INCLUDETEXT fields is that the content linked from the source document can be updated in any of the related documents.

Note: With Word's field code display toggled on (e.g. by pressing Alt-F9), you'll see a field code that looks like:
{ INCLUDETEXT "C:\\Users\\Dingo\\Documents\\Source Document.docx" BkMk }
where 'BkMk' is your bookmark's name. By simply copying & pasting the entire field, the simple expedient of changing the bookmark's name in the field code means you don't need to go through the steps at 4, above, for every link. When you're done copying, pasting & editing, simply press Alt-F9, then Ctrl-A, F9 will refresh all the links.

For more on INCLUDETEXT fields, see: Field codes: IncludeText field - Office Support

If you want to make the links between the source and related files portable, see: https://www.msofficeforums.com/word/...nal-files.html

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]