Hide Content in Mac Preview Screenshots

I was looking for a quick way to blur out sensitive information in a screenshot using Preview on a Mac. While I didn’t find an actual blur tool, something can can accomplish the same thing is simply drawing a box around the area you want to hide and pressing delete – see screenshot below where my Access Key ID is whited out:

Screen Shot 2017-08-08 at 7.36.11 AM

This seems to only work in image files, not pdfs.