There are programs out there that will take a scan, any scan you make or a pdf, and convert that image into a notation file. Neuratron is one business, if that's the right name. Photoscore or something like that. I've used it a few times.
Except they don't always convert perfectly. Like 90% of the notes are correct and then it has no idea what that slur actually is.
So if you get good using it, it's useful.
I think I took a Clementi sonatini off here, converted it to notation, then the notation to MIDI, and had the MIDI play back. Essentially, the computer played back the direct printed music. It was kind of freaky and it didn't have too many errors because it was fairly straightforward notation. My test was succesful, but I didn't know how to go about fixing all the errors.