Apple Preview, Scanned Documents, and Links

I read today of someone reporting problems of Mac users not being able to see colored text or an underline for links, but are able to click on them. It looks like this is a problem with Apple's Preview, as things look fine in Adobe Acrobat. I haven't seen anything suggesting a problem or a fix. This appears to only happen with a scanned document that then has links added to it later. Using a scanned document has the added difficulty of the words being an image as opposed to actual text, so the PDF file will be of no use to the blind.