These are two separate things. So,
1. For scanned JPEG files, use the Image>Adjustment>Shadow/Highlight tool. Works pretty well, and it's the quickest and easiest solution.
2. If you are doing the scanning, you can get better control over your scans, but it takes more work. Do your scans at the highest quality and save them as 16-bit TIFF files. Then use Bridge to open those TIFF files using the Camera RAW interface. (File>Open in Camera RAW)
You will find that you have more "headroom" to work with exposure, fill light, etc., using a 16-bit tiff file.