The Internet Archive does this a lot. There was an old 90s book that I needed but they never made an electronic edition. So the internet archive, scanned and digitized it with character recognition to make a select-able PDF like this, as well an epub that can be read on your phone like any other ebook.

Now that book is available for anyone to borrow and read. (its still copyrighted so you gotta access it via their DRM controlled app/website, but that can be easily broken and its better than not having access to that book at all)

Google runs its own OCR pass on scanned PDF documents in order to index them better. It can be annoying when you get a 50 page scanned document as a search result and then find out that it doesn't include a text layer, so you need to run your own OCR or skim the whole thing to find the relevant parts.

https://en.wikipedia.org/wiki/Optical_character_recognition

One of the few applications where ML-based image recognition actually works reliably enough for real-world applications; the USPS has been using neural nets to read zip codes for decades.

It's quite common. A combination of scanning + OCR on the same PDF.