Detect and remove margins in each page in a PDF file. More information: https://github.com/ho-tex/pdfcrop.
pdfcrop path/to/input_file.pdf path/to/output_file.pdf
pdfcrop path/to/input_file.pdf --margins 'left top right bottom' path/to/output_file.pdf
pdfcrop path/to/input_file.pdf --margins 300 path/to/output_file.pdf
pdfcrop path/to/input_file.pdf --bbox 'left top right bottom' path/to/output_file.pdf
pdfcrop path/to/input_file.pdf --bbox-odd 'left top right bottom' --bbox-even 'left top right bottom' path/to/output_file.pdf
pdfcrop path/to/input_file.pdf --resolution 72 path/to/output_file.pdf