Loosing hatches when exporting to PDF

If I export my CAD drawing to PDF or if I print to a PDF file (using Microsoft's print to pdf or CutePDF writer) I loose all hatchings.

I am using Version:
2.1.3
Compiler: GNU GCC 4.9.1
Compiled on: Sep 23 2016
Qt Version: 5.4.1
Boost Version: 1.60.0
System: Windows 10

Any advice gratefully received

Does this happen also when you do a real print? How does it look in 'print preview' mode? Is the layer with the hatchings set to 'construction layer' (double lined cross)? These are meant as auxiliary drawing aides and will not be printed.
Otherwise I can't think of a reason. What's the line width?