Corrupted files I need to "uncorrupt" without deleting the files themselves...?

I am reading online about how to do this, if possible, but any expert opinions would be appreciated very much.

The corrupted files are on a fat-formatted flash that i'm using on debian. The current files that I have found with corruption, though there may be more, come from documents that were 'scanned' and saved to the flash. I can see part of the document, but the other part of the same document looks like there is a 'dark, solid gray piece of paper covering the rest of the document; in most cases, most of the document is covered starting below the top of the document.

Any direction regarding this would likely be helpful!

Thanks.