It sounds like the file you're working on doesn't contain actual text, just an image with text in it.
If you have Acrobat try running Text Recognition on it, from the Tools panel on the right. If you have the free Reader there's nothing you can do about it.
It turns out, this did solve my problem. Although the document is generally a normal PDF, a short stretch of it was an image. After I moved past that area, everything works normally.
Strangely though, even in that section, I am able to select any area for a snapshot. One would expect only the entire area to be selectable.
I tried to click “correct” but there is no such button. However, Thank you for your help
I marked it for you... And glad to hear you were able to figure out what was going on!