Master Document with Hyper links

Sorry for the long setup to my question:

I am tasked with creating a Master Document that is composed of a set of Sub Documents (almost 100 sub documents).

When completed; the Master Document (a set of links to the sub documents) will be further exported to a PDF file.

Prior to linking the documents together; the Sub Documents are in a collection of hierarchical tree of sub directories.

I am already aware that the ODT->PDF conversion will drop any Table of Contents (TOC) and substitute its own links.

However, what is still needed is the means by which text in one document can link to text or a Header in another document and most importantly, how to maintain this linkage though the ODT->PDF conversion process?