Craft CMS 3 data structure advice for vehicle make, model, trim, year tagging
Goal: Filter documents by related vehicle characteristics.

My first idea would be to create it as such:


Create an assets volume where all your documents will be uploaded to.
Create a vehicle category group for your vehicles such as you already defined (the structure you mentioned)
Add 2 fields to the assets volume:


Vehicle (category field)
Year (date field)



This will allow you to add the relevant data to each document. You can than display the documents on your frontend and search/filter them by category and/or date. 
How you do that is up to you, either with Twig serverside or with VueJS for example client side.