Length: how long each mark is.
Offset: the gap between the edge of the artwork and the start of the mark. A minus number makes marks inside the shape.
Bleed: how much bleed the selected artwork includes. The marks line up with the trim (that far in from the edge of the selection). Use 0 if the selection is already the finished size.
Style: eight styles of mark: Standard, Standard+Corner, Corner, Cross, Jap, Center, Center-Vert and Center-Horz.
Positions (the square of tick boxes): choose which marks to make: each corner, and the middle of each side.
Apply to multiple shapes individually: select several shapes and each gets its own crop marks.
Create Layer: put the marks on their own layer (named on the Settings tab).
Add Outline: a white outline round each mark, so it shows on dark backgrounds.
Dashed Lines: dashed marks, for fold lines.
Create corner crop marks: marks at the corners of the artwork.
Detect and add crop marks to straight lines in single shape: select one shape (such as a triangle) and get a mark at each end of every straight edge, so odd shapes can be cut accurately.
Frame: draw a rectangle at the Trim, the Bleed, the Inner Crop (where the marks start) or the Outer Crop (where they end), or None.
Resize artboard to crop marks: fit the artboard your artwork is on to the outer edges of the marks.
Add Cropmarks: does it.