Is an index useful in a PDF?
In a world of digital documents, is an index still an essential part of good technical documentation?
Full-text search seems to have replaced it. Technical manuals are rarely shipped to customers on paper anymore; PDF has become the norm - an odd little format that sits between the source (which customers never see) and an increasingly rare printed copy. Hitting Ctrl+F is now second nature for anyone hunting for information.
Content written for the web leans on a wide vocabulary to improve its visibility in search engines, and synonyms are essential: they give readers several routes to the same information. By that logic, search has made the index obsolete.
Except that the logic reverses when documentation is terminologically consistent. If the technical writer only ever writes directory, a reader searching for folder comes up empty - and the more disciplined the terminology, the worse full-text search performs.
That is exactly when a well-built index earns its place. The catch is the effort it takes, concentrated at the very end of the project, right before delivery - and a sloppy index helps no one, neither customer nor company.
So there is a paradox: an index is more useful for high-quality documentation than for inconsistent documentation, yet its cost-to-benefit ratio is low. It is a luxury few companies can justify, and not the first thing quality should buy. An index is the icing on the cake of technical documentation - but what matters most is the cake itself.