When reviewing your PDF file you may notice very feint white lines on your cover or book interior pages. These “hairlines” are the result of the transparency flatteners used to create PDFs, and sometimes appear around the edges of text and images boxes.
Please note, these line will NOT print when your book is produced, they are only visible on your computer screen.
By zooming in and out, you can see that the lines are not real lines drawn on your PDF. The lines can disappear and they do not get any thicker when you zoom in – the line is always only 1 pixel wide. The thickness of a real line would increase and decrease as you zoomed in and out.