Searching for text in a PDF

I am a newcomer to Scriverner. I bought it in the hope that it would help me stay organised whilst I write my first ever dissertation.
I have come up with a problem that I have been unable to solve and hope somebody can help me out.
I carried out a search for a couple of words in all my imported PDFs. The list containing those words appeared in the binder in a separate collection. Howerever, when I open those PDFs the text that I was looking for is not highlighted. I therefore have to open the files in a separate viewer and search again, or painstackingly rin through pages of documents looking for those words.
Is that normal or is there a way to highlight the text being searched for?
I hope that is clear.
Thankyou for helping me,
Kind regards