Check and see if your scanner software gives you the option to recognize text during a scan. Software that does that is called OCR software (object c.... recognition). If it does not have that option, then there are programs out there that will look at an image and extract text from it. The best one, in my opinion, is Abbyy Finereader 9.0, but it is really expensive. You can also google for "OCR software".
Saving as pdf does not automatically mean that it will recognize text. It just means that it could save the whole thing as an image in a pdf file. When the text in a pdf file is properly recognized then you can zoom in a lot and the text will always look sharp. If the text is recognized just as an image, then when you zoom in, it will start getting really blurry. You will also notice the difference in clarity when you print it.