When you "scan" a document into a computer it creates a bitmap image. To
enable Word to edit the scanned document you need to use an Optical
Character Recognition (OCR) program (similar to Office Document Imaging in
some versions (don't remember but don't think it is in all versions) of
Office 2003) or the one that may have come with your scanner.
If you don't need to edit the scanned document, you can insert it as a
picture in the Word file and it will appear. Save it as a .bmp, .jpg. or
..tif image in whatever scanning program you are using first and then click
on Insert, Picture from File in Word.