Printing in black and white problems

Hi

I am trying to print off a PDF from adobe reader. I am trying to print in black and white.I am using a mac book air.

The greyscale colour option is greyed out and checked, which is fine with me as even though i am unable to edit it, I WANT it in greyscale. If i click on the advanced button, it is all greyed out and all options are unable to be changed.

The image preview in the bottom right hand corner shows the image in black and white - which is what is wanted.

HOWEVER, when I then press print, it prints in colour? I have tried changing preferences and all other suggestions which I have found online. I just want to print in greyscale and not colour and do not understand why this option is greyed out for some PDF's and not others - 10 minutes before I was able to print one in black and white?

Any help would be appreciated - it is driving me crazy and I really REALLY need these documents for Uni work.

Thank you