In SharePoint it is known that a workflow can be added to the document library. Is there a way to create a SharePoint Designer workflow to apply to one or two documents in the library not the whole library? Is it best to use a SharePoint Designer workflow or out of the box workflow?
You can trigger the workflow on item creation or modification bur executing the actual workflow logic (action) write an if condition like - if filename equals (or some other criteria) "This file" then perform your rest of the action, this way we can execute workflow action based on the attributes. However, if you have a third party product like Nintex - you can even trigger the workflow conditionally, on the specific item.