Why this is the hardest thing to hold across a long document
Capitalization decisions are invisible one at a time and obvious in aggregate. That is why they survive proofreading and fail on a second reading.
No reader notices the fourth appearance of a capitalized job title. Every reader notices when a document capitalizes Director on page 2, director on page 40, and Director again on page 90. By then they are working out whether the three are the same person.
There is no authority that settles it, because the question is usually about this organization rather than about English. A company deciding whether its own departments take capitals is not consulting a manual. It is making a decision, and then needing to remember it across every document it publishes for the next several years.
Where the rules do supply an answer
Three places do supply an answer, and they are worth knowing because they end the argument rather than continuing it.
A title in the second person is capitalized.2 Your Excellency, Mr. Chairman, Madam Chairman. Conversational salutations are not: my dear General, my dear sir.
In formal lists of delegates and representatives, all titles and descriptive designations immediately following the names are capitalized if any one of them is.2 That is a consistency rule rather than a capitalization rule. It is also the one most often broken, usually in an appendix nobody proofread twice.
Product and company names follow the owner's usage, with the generic part kept lowercase, which is also how a regulated label treats them. Chicago's example is Scotch tape.1 An editor checking a product name is checking it against the manufacturer rather than against a dictionary.
The pass that finds the inconsistencies
Reading does not find them, because the eye supplies the form it expects. Extraction does.
Every capitalized word that is not at the start of a sentence is listed, with its context. Every job title, department name, product name, and internal program name is grouped so the variants sit together. Terms appearing in more than one form are the finding, and on a long document there are usually more of them than anyone expected.
Editors Canada places this inside copy editing. The standards cover resolving variations in terminology, logic, and mechanics, and maintaining the style sheet that records the decisions taken.3 The definitions put the same work under checking mechanical consistency.4
The style sheet is what makes it stick. A capitalization decision that exists only in an editor's memory has a life of one project, and the next editor starts the inventory again.
Where the client decides
An editor does not decide whether an organization's departments take capitals, what a product is called, or how a company refers to its own officers. Those belong to the client, and where a house guide exists, to that guide.
What an editor supplies is the inventory of every variant currently in use, a recommendation where the chosen manual settles the question, and a query where it does not. Everything a client sends is treated in confidence, including internal documents, drafts, and correspondence.
We work on corporate documents and website copy to whichever authority a client names. The style sheet comes back with the work, so the decisions outlive the project.
An organization that has never written its capitalization decisions down can find out how many it has in twenty minutes. Search a recent report for its own department names, and count the spellings.