[Feature request] Automated Crop by detecting white space and trimming pages

[econo202]

It'd be great if it was possible to set crop margins by value (separately top, bottom, right, left) in selected units, not only by hand.

[julianmueller]

A very nice addition to the crop would also be an "automatic crop" that crops all the whitespace around the content of the pdf. Maybe with a whitespace padding option, that the content is offsetted when auto cropping.