Here's the sitch: The company I work for has a site collection of a few SPO sites, with most traffic coming to their "main" site. Other than SPO's default metadata (which we don't use other than for out-of-the-box features), we've not used much in the way of metadata before. However, when I told them about the possible benefits of "tagging" files with Managed Metadata (or rather, what you can use it for), they became interested ... which means I've found myself in charge of finding out what our options are.
Essentially, I'm looking for a way to, after adding a Managed Metadata column to the default Document (and possibly Page) content type libraries, bulk tag every single document authored by certain people with forms of "official document" metadata tags related to their departments, regardless of where they're stored, using this column (and terms prepared for this purpose in the term library).
I admittedly have little PowerShell experience, but I can learn, if that's what it takes.