If you want to be able to modify the text, it'll take some sort of OCR software to convert the picture that is scanned in, into a text file.
I've been using OmniPage Pro, but have upgraded to the X version yet because I don't want to buy a new scanner (no twain widget support in X), and it works in classic anyways.
Because of the current state of scanner support in OS X, matching up scanners and OCR software is a bit more difficult than OS 9.