When you scan a document, you are normally given an option as to the "type"
of document (or how you want it scanned). If it contains text, a decent
scanning software will recognize it and offer to scan it into Word. If your
document (text) got scanned as an object (image), you can't edit it (since
it isn't text).
Try scanning again and make sure the type is set to "Text" and see if it
scans it into Word, where you will have a chance to edit that text.