It depends on the quality of the scan, the font of the printed text, and how well the printed material has held up.
I recently bought a new HP 5740 printer/scanner/fax combination. It came with an OCR program called I.R.I.S, that does a reasonably good job of converting the image text to digital text. I used it recently it to OCR a paper budget report. I was able to paste the resulting digital document into a spread sheet with minimal errors.
Remember once you get the digital text you will have to put it in a searchable database.
From experience. I find that even though the original is in black and white, I get a better image if I scan it in color. Also when you scan a black and white image in color it seems that the OCR programs perform better.
I will not mention any names but the Allen County Genealogy Society of Indiana ACGSI.org, does this routinely. You may wish to contact them and get better hands on information that I can give you.