Why are jpeg & pdf documents being covered with solid black rectangles? There are specific pages of legal documents that I scanned myself as jpegs then combined in a pdf yesterday and they looked great. I downloaded it back from iCloud and they show up in the application for maybe 0 to 1 frames before a black rectangle covers up all the information in the document. Then I opened some jpegs that have been only on my computer since scanned, and they get the same censoring effect. I think I'll make up the term dynamically redacted since the redacting is being done by the application when displaying the otherwise non-redacted file. For further evidence as requested by a commenter, I also moved the file that Preview was redacting into iCloud to test it with my iPhone and was able to view the file normally with the iPhone. 

Here is the problem occurring in Preview with a local pdf document.


Here is the problem occurring in Finder with local jpeg files.


Here is an example depicting more concretely a comparison that the documents are being observed sometimes normally and sometimes they are censored. When I attempted to take this final image with grab it refused when I selected Preview as a window and said that "the contents cannot be shared."


So far, I've noticed that the censoring affects Preview and Finder so it must be an Apple system-wide protocol. Grab probably is just inheriting the message from the window that it tries to grab from. 

Update
It may be interesting to point out that the pages that are redacted are exactly the ones which I scanned using the document feeder and not the ones using the flatbed of the scanner. So, it could be possible that the scanner is somehow setting a setting for the pdf files based on how they are scanned. The scanner was a Brother MFC-7460DN

Update 2
It appears as though I found the culprit setting. Notice that the infos with color show the preview image while the ones set to grey do not. This fact applies to the other examples as well. Apparently, it is simply how the applications handle previewing greyscale images vs. color.
It is a result of how Apple implemented the display for Preview and Finder which depends on whether the jpeg or pdf has the property of being a color image or greyscale image.