I tried it with one of these image-based PDFs and didn't get it to work. Is this Apple-Silicon-only? Or is there any other step you need to do?
Edit: As of July of 2021, Live Text was available in beta on Intel Macs so by the time Monterey shipped it worked on both Intel and AS.
Whether it works on a given document may depend on how that app displays the image. I can see where it would be complicated in a PDF where you may have combinations of text, images, and OCR’d text behind images.
It works with anything that works with Monterey. So if you are running macOS Monterey you fit the requirements.