I recently needed to search for a string enclosed in square brackets in a PDF document. So I typed
[concept] into the search field (including the square brackets).
The result surprised me, as I got a list of pages containing the word
concept with all letters contained in that word highlighted in yellow.
I haven't been able to find any documentation of this "feature" - or any other special syntax in the search field.
What is the straight explanation for this behaviour, if any?