There is no setting that will allow you to print your board at the
center of the page, the only work around is for you to place a dot at
the top left corner of the board. By doing this, Ultiboard will push
you design toward the center.
If you need the fuducial marks to show on the print, export Gerber files and reimport into Ultboard be select File--Open and pick the gerber in the file of type field.