A lot depends on the quality of your hardcopy document. Assuming your original document is printed rather than handwritten, I'd probably start with an OCR package. For "garden grade" stuff, you can often do pretty well with the HP multi-purpose (printer/scanner/fax) machines. If you have more demanding needs, you probably want to use one of the higher end flatbed scanners with better OCR software.
Depends on the volume of information, the quality of the paper and degree of contrast between the text and its background. I find the ability of scanners and OCR software amazing for many tasks, but it still has problems with columns of text or numbers, text flowing around images.
I have had good results on a £30 USB flatbed scanner with the bundled OCR package (I think it was Caere not sure). Certainly worked for documents, however had real problems on reports it get getting confused as to how to handle columnar or row data.
The general conclusion was that in many cases it was quicker and more reliable to re-type.
Of course there are potential copyright issues if youa re not the original copyright owner.