Accurate time estimates for software development are notoriously difficult to achieve, especially if there is no precedent for the software being written.
Conventional ways of addressing within a document (page numbers, chapter/section/paragraph numbers) are brittle and will break with changes to a document's content—or even its formatting.
Digital document formats tend to have stable identifiers for addressable elements (at least scoped to the document itself), but they tend not to expose these.
The net value of the result of a given endeavour should be greater than known alternative endeavours (i.e., what you could have done instead of what you did).
Or, if the document format does expose its internal addressing mechanism (such as with HTML and PDF), it's up to the author to manage the sub-addresses.
While tables of contents, bibliographies, and indices can be reliably generated, moving content around breaks all but coarsest-grained references from other information resources.