On a copier or scannner yes. You play with settings until you are able to get the most readible results. I've done it many times even with newer non-thermal faxes.

And you will have to dink around to find what works... there is no universal do exactly this and it will work. As you darken it you WILL be darkening other stuff that will make it harder to read... and you have to find the right balance in your specific situation.

Scanning is the answer try using colored transparent sheets to act as filters if enhancing the brightness and contrast do not get you enough detail