The settings under the Paper tab govern the paper color and the many visual aspects of the finishing marks.
Although most settings are straightforward, some settings merit separate mention:
The Paper Color defaults to white, which is equivalent to a transparent paper background, any other color set here will be painted onto the page before drawing the contents.
Force Inner Marks can be used to force the rendering of trim and/or bleed marks in layouts that specify groups of columns and/or rows, and where the inter group gutters are not large enough to easily accommodate these marks.
The Gap specifies how much space to leave between the edge of the page and the start of the mark alongside it.
The Inset specifies how much to inset (move inward) the mark from its default location. Without inset, bleed and trim marks tend to overlap where they both occur. The inset is mostly used for trim marks to indicate the location where the printed media is to be cut to size.
When trim or bleed marks settings specify the Per Slot setting, the marks are derived from their corresponding display boxes (bleed or trim box) on the page of each slot, and the inset values are applied when rendering the marks. When manual setting is off, the marks are derived from their corresponding display boxes on the sheet.
Manual trim/fold marks, derived per slot.
Automatic trim/fold marks, derived per sheet.