Looking for advice
I wish to create a single editable document approx. 4-500 pages
From this document I wish to produce multiple documents, from the single editable document. Each Document comprising of parts of the original editable document
Now my problem is that I have no idea what to call this so that I can google it

The Document I’m referring to is a business operational manual, so the editable document is constantly changing with policies and procedures, and multiple Documents will be for different departments (most will share similar pages, but all will be different)
So I’m trying to find a way I can a create a header, index and link to each page. With the hope that this Document can be printed out in PDF with out update each sub document each time.

Is this something that I can create in Word and export to a PDF convertor?

All feedback welcome

Look into AutoText.
Automated Boilerplate Using Microsoft Word
Use AutoText Fields in the derivative documents.

There is nothing in Word that does exactly what you want. I think that is the closest.
Probably the Office program that would do what you want is Access, but that presents a very steep learning curve.

If you are going to keep a single document, look at:

• How to create a table of contents in Microsoft Word by Shauna Kelly
• Why use Microsoft Word’s built-in heading styles? by Shauna Kelly
• StyleRef Field for your headers
• Moving/Reorganizing Pages in Microsoft Word
• You do NOT want to use the Master Documents "Feature" in Microsoft Word

I don't see anything in Charles' posts that seem to align with what I thought you asked so I could be off on a tangent.

This is called "single sourcing" and it is possible in Word but it requires some knowledge to set up correctly. There are other software products are more focused at this (AuthorIT or MadCap Flare) but that is possibly more because the user base of technical writers do this as their daily job and understand it better. Word can also do it as long as you understand the principles and can make use of macros and fields or content controls.

"Single sourcing" is a catch all term and can be at enacted various levels. For example:
Language localisation: Same doc but with individual words spelt differently eg Australian reader sees colour, analyse but US readers see color, analyze.
Content: As you have described, document contains lots of modules/chapters and you want to produce variants by showing/hiding modules according to which reader needs it (technical user guide vs quick start vs marketing guide)
Output Format: Mobile vs Web vs online help vs Printed vs PDF. For instance, page numbers in the TOC make no sense in Web or help versions but do in print and PDF output.
Theme: imagine day/night view of google maps - same info but different look for different situation/viewer groups

If I was doing this job and working at the Content level as you asked, I would be putting each module into a Rich Text Content Control and tagging each one and then using a macro to show or hide the ranges according to the user's preference and rebuild the TOC before outputting to PDF.

__________________
Andrew Lockton
Chrysalis Design, Melbourne Australia

@Andrew

My first suggestion was to develop a template holding the individual parts as AutoText and then using AutoText fields in separate documents for those purposes. Whatever method is suggested, it is going to be a kludge compared to purpose-built software. On the other hand, I do not know of any purpose-built software with Word's formatting power.

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]

That's hardly an effective solution for:
I beg to differ.

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

@Charles
You don't need other software to do this - it can be done cleanly enough in Word but there are a variety of methods that can be used depending on what exactly it is that you want to achieve.

Paul's use of IncludeText fields is a robust method that essentially does what Master Document's was meant to achieve. I'm not convinced that numbered lists will avoid running on but apart from that possible wrinkle, this is a clean (and non-macro) way of modularising and single-sourcing the content.

With fields, you can also show/hide content by using document properties and IF fields eg
{If {DocProperty "Language"}="Australian" colour color}
This can work cleanly on a small scale with individual words and it can also be extended to work on large chunks of content but but it will become more and more problematic to edit with large content or non-binary choices.

Because the source document already exists, Paul's described method will likely give the fastest possible workable result.

__________________
Andrew Lockton
Chrysalis Design, Melbourne Australia

Indeed, I've been recommending the use of INCLUDETEXT fields instead of 'Master Documents' for over a decade, as well as for exactly the kind of thing the OP is trying to achieve.
To the extent that it's relevant, whether automatic numbers in the source re-set in the related document can be controlled via the INCLUDETEXT field's \! switch.

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