Check your Cell size (Print Module). For the print to be centered on the page the Cell size within which the photo is contained must be coherent with the paper size and the margins you set in the Margins panel. The size of the paper you feed into the printer must be the same as the paper size you specify in Page Set-Up. So for example - my usual case, I use Super A3 (13*19 inches). The width of paper being fed into the top feeder is the 13 inch dimension. I want one inch margins on each of the four sides. That leaves me with a Cell size of 11*17 inches maximum (i.e. 13 - 2 x 19 - 2) for the photo. Set up this way, the photo is centered. It will not fill the whole cell if the aspect ratio of the photo differs from the aspect ratio of the Cell. In this case, it will fill up to the limit of either the height or the width and there will be an equal amount of white space on either side of the other dimension.
