Rulers are displayed at the top and left of the [Preview] view. The units displayed in the rulers depend on the [Region] setting (inches / mm).
Guidelines can be placed in the [Preview] view by dragging them from the rulers
Horizontal ruler: horizontal guideline
Vertical ruler: vertical guideline
Intersection of horizontal and vertical ruler: horizontal and vertical guidelines.
You can exactly position a guideline. Click [View] - [Add guideline] or double-click a ruler. A dialogue appears that allows you specify the exact position of the guideline. Click [Edit] to select a colour for the guideline. You can save the defined guidelines as default guidelines. Click [View] - [Save as default guidelines]. You can apply the default guidelines to any document. Click [View] - [Apply default guidelines].
Right-click on an existing guideline to edit, centre, or delete it. Show or hide guidelines:
Option 'Show guidelines' in menu 'View' is automatically enabled when you add a guideline.
Click 'View' - 'Remove all guidelines' to delete all guidelines from the [Preview] view.