Blue Box Outline appears when using Find Functionality

Many a time when we search for a word in a PDF, Acrobat/Reader highlights the word, but the selection size is extremely small in size which makes it difficult to find where the highlight was done. For such cases, Acrobat/Reader has a feature known as “Halo affect”. If the text selection size is below a threshold, a blue rectangle is drawn with the selection in the centre. This makes it easy for the user to find the highlighted text. See snapshot below showing how the halo rectangle looks like.

The halo rectangle works as a zoom-in function. Clicking inside the rectangle will zoom-in with the selected text in the center. Also, if the PDF is "zoomed in" so that the text selection size increases beyond the threshold, the halo rectangle automatically disappears.