Invisible space in the text
Open the attached document, which is a dishwasher manual, in Acrobat reader, and search for the word "floor". It will not be found. However, it's present in the document on page 6 in the bottom of the left column.
In Reader, go to the page 6 and copy to clipboard the line beginning with "When the GREEN LIGHT"'; then open Notepad and paste. You will see the space in the middle of the word "floor".
So it looks like the text has a space in the middle, although the word appears in Reader without the space. This makes more difficult text operations and search.
Vadim Rapp shared this idea