How are you scanning and opening the document? Most scanners default to scanning things as an image (BMP or JPEG file).
If you've already tried the following, my apologies: what you need is an OCR (
Optical
Character Recognition) program. Depending on what version of Windows/Office etc you have, you may already have Microsoft Document Imaging (information here:
http://www.pcmag.com/article2/0,1895,1832750,0 0.asp ). Your scanner possibly came with an OCR program (often a cut down version of ABBYY Finereader) or you could try SimpleOCR which is free/donationware from here:
http://www.snapfiles.com/get/SimpleOCR.html (never used it myself).
The above programs will then try to convert the images the scanner creates into text. They tend to work best with black text on a white background and a good, crisp scan. Better OCR software will even try to convert handwriting. In my experience (though I've never used one of the expensive commercial packages) it tends to be a bit hit-and-miss and even when it has done a good job you will still need to check and edit the work.