There are black lines and boxes in the eBook

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!