[runaib]

Thanks Mike.  I know all that - I'm pretty sure there's no non-white pixels where the vertical cropping is stopping because the PDF is generated from Microsoft word rather than scanned in and is structured internally mostly as PDF text.  Although there are sometimes images embedded in the document, the last line is always text, so after that it should be all white space with no non-white pixels.  In my case, I don't need to crop horizontally, as I already have the word document set to the width I require, so its just the vertical cropping I am having problems with.  Typically its cropping about half of the white space rather than all of it.  (I've got cases where there are only 4 cm of text in a 39cm liong document.)   I was wondering if there are limits to your crop scanning and it just stops doing so after scanning a particularly large area full of white pixels.