When you scan something you are basically taking a picture of it, to get it to be editable you need something that will "read" the picture and convert it into real text, this is called optical character recognition (OCR).
There are loads of free bits of software or online services that will do this, but they tend to only work well with clear, typed or printed text, you've not got a hope in hell of them working well with hand written words. (and even if you are converting from printed text read the results very carefully because OCR does make mistakes)
There is an online OCR service here
http://www.onlineocr.net/



