Available in pre-release 3.7
Usage: SumatraPDF trim [options] <input filename>
  -b -    Which box to trim to (MediaBox(default), CropBox, BleedBox, TrimBox, ArtBox)
  -m -    Add margins to box (+ve for inwards, -ve outwards).
                  <All> or <V>,<H> or <T>,<R>,<B>,<L>
  -e      Exclude contents of box, rather than include them
  -f      Fallback to mediabox if specified box not available
  -o -    Output file