Prepare
Cut every page down to its trim box, its bleed box, or by a margin you set. The boxes are read from the file, so a press-ready PDF crops itself.
One click removes printer marks and slug from a press PDF.
Crop to the bleed box when the next step needs it.
Take a fixed amount off every side, in millimetres.
The defaults come from your file. Change a setting and the proof updates before you let go of the mouse.