I am unable to export my Lightroom book to PDF or Blurb. I receive, 'An error has occurred adding text and fonts to the book'. I am not using 3rd party fonts.I am on Windows 10 on a laptop with 8Gb RAM. The book is 206 pages and the error message appears when rendering page 192. I am on Lightroom 5.7.1. Can anyone help me please?