If the PDF text on a page has non-printing control characters in it, then when the find dialogue is used, some of the highlights for matches maybe incorrectly located/sized depending on their position relative to the hidden characters. This is rooted int he fact that PDFium's API for getting text from the document doesn't clearly distinguish between the index in the visible text and the index in the underlying text stream.

The attached doc has some non-printing characters, so the highlight for 'around' on the first page will be incorrect.