I found that all PDF's I tried so far could be cropped manually by editing the MediaBox.
For example, an A4 PDF will contain something like
/MediaBox [ 0 0 595 842 ]
in one or several places. I just adjusted the four values - to crop 50 points from each border, I'd change that to
/MediaBox [ 50 50 545 792 ]
Both acroread and xpdf will honor that. That way, you can even crop page numbers / chapter headings and such away.
Under Linux, I'd do it using sed:
sed 's/0 0 595 842/50 50 545 792/g' <book.pdf >cropped.pdf
Under Windows, you'd have to open the pdf in notepad or something (don't know if that harms binary streams in the pdf)