I suppose that you're dealing with a PDF file without text layers (it might be a scan or a flattened copy where the text is perceived as a solid image). To check this, please try to select a text fragment of your document in any other app, in Preview for instance. In case the text selection doesn't work there either, it means that your file needs to undergo an optical character recognition (OCR) first and only then it will work in PDF Reader Pro properly. The OCR feature will be available in one of upcoming releases of PDF Reader Pro for Mac. Plus, OCR for PDF Reader Pro iOS is available now.