The text is question is being painted but using white as the fill colour. The colour space for this block of text is Seperation and has a rather strange definition:
[/Separation/Auto/DeviceCMYK 21 0 R]
/Auto is defined as the named colour which is strange as there is nothing in the specification about how handle it.
I've added a new rule in Rule in our Separation colour class to convert /Auto to /Black. I'll run this through QA to see if there are any side effects but suspect this will be fine for a one off PDF.