Info-Mac

I scan a doc to my I-Mac and then send via email to a P C user but they cannot alter the doc in any way. How do I make it so that it can be revised?

Well if it's an image, you can't. You've simply scanned a photograph of your document. You'll have to either type it out, or try using Optical Character Recognition (OCR) software. Most scanners come with some. Or you can try looking at some OCR comparisons online like this one. I myself don't have any experience with OCR software so I cannot offer any recommendations.