InDesign Index for Existing Catalog

[Shantelle5CC9]

I've watched a couple of tutorials about creating a Linked Index (page numbers in Index shift with linked item in content) but is it possible to do that with a Catalog that has already been created?

Here is our digital Catalog ( https://online.flippingbook.com/view/561708532/ )...that we want to fix/correct the Index that's already present. Is this possible?

[Eugene Tyson]

How was the index originally created? Was it manually created? Used an a 3rd party company to generate the index? Was it created in InDesign? 

How do you predict the updating of the index?