This is a known issue with the default PDF viewer in Mac OS 10 and the PDFs created with Microsoft Word (which I use to create my PDFs). The way to resolve this is actually quite simple:
(1) Make sure your Adobe Reader version is updated. You can download it for free at https://get.adobe.com/reader
(2) After you download the PDF, open Adobe Reader first. Then from within Adobe Reader, open the PDF file.
If this still doesn't resolve your problem, please contact us!