Cropping PDF files

pdfcrop --margins '-10 -20 -30 -40' input.pdf output.pdf

{Command notes: left, top, right and bottom margins of -10, -20, -30, and -40 pt (points) respectively, input file input.pdf, output file output.pdf}

Re-sizing PDF files

pdfcrop --margins '10 20 30 40' input.pdf output.pdf

{Command notes: left, top, right and bottom margins of 5, 10, 20, and 30 pt (points), input file input.pdf, output file output.pdf}

Standard-sizing PDF files

pdfjam --outfile output.pdf --paper a4paper input.pdf

{Command notes: a4paper gives a standard a4 papaer size to the output file, input file input.pdf, output file output.pdf}

A personal technical diary… To the point… Precise