Crop PDF
Cropping a PDF document using Goshtscript:
./gswin64c.exe -o outputPDFFile.pdf -sDEVICE=pdfwrite -c "[/CropBox [0 50 800 1000] /PAGES pdfmark" -f inputPDFFIle.pdf
For understanding how the crop box's dimensions work, visit:
http://stackoverflow.com/questions/5797841/cropping-a-pdf-adding-crop-box-using-ghostscript