Level transparency ignored when plotting to pdf


I'm using Microstation Connect Edition and i'm trying to create a plan with referenced ariel photography (full clour no transparancy) and intend to overlay levels of lines and text and a level of contours at 50% transparency.

The image beow shows the ideal look in the model view:

However when i print the pdf  from a sheet viewwith transparency checked the levels come out solid. 

I have noted other solutions of rasterizing the plot but this creates a low quality print which is not acceptable

I have tried a plot config with a Pen table suited for this level and colour but no joy.

Anybody have any other ideas?

Many Thanks