In addition to what everyone else has said,

>Or do you print . . . in order to see what it will look like and adjust?

Many printing/publishing companies have special laser or inkjet printers that have been specially calibrated using a standard called SWOP (Specification for Web Offset Publications; not "Web" here refers to web press printing not the world wide web) to closely mimick what something will look like on the industrial scale printing presses. In the early days of my publishing career, I worked on paper page proofs made by a normal mediocre quality office printer and also got a stack of high quality SWOP proofs just of the art.