Thanks for all the suggestions. I think my problem stemmed from the use of MS Word (which doesn't surprise me). Even though it allows custom page sizes, it somehow tricks the pdf printer drivers into printing to A4 if the custom page size is very small. If I use a non microsoft applications it seems to work OK.
I figured out what was going wrong with pdfcrop. As a first time python user I was making an embarrassing mistake. Windows users of python can find some tips here http://www.python.org/doc/faq/windows/#how-do-i-run-a-python-program-under-w indows I have not persevered however, because pdfcrop does not do quite what I want (according to it's supporting documentation). Bruce
