Allow us to declare on the doc if it relates to any of the mentioned objects (or multiple).

Then ADD to the target object an icon indicating there's a doc linked to it. If there are multiple docs allow a drop down with a list of all the linked docs. The icon or drop down should provide quick links.

This will allow users to know when there's a doc relevant to what they are working on and to get to it quickly and in context (will make "checking" the knowledge base redundant).

E.g.

I've added some docs in regards to client A and I've linked them to a list where we keep all client A's tasks. Now all other team members could see I've added the docs and quickly navigate to "guidelines", "launching a new product", "new" etc. quickly and without me needing to make sure they know the docs exist