Poser 5 is a little inconsistent. File|Export give an option for the picture, with the usual Windows-style methods to pick imagefile format. If you render to a new window, which you need to for a large image, you have to use File|Save_As. And Save/Save_As sometimes offers to save the picture as well as the .pz3 file. For some images a tweak to the brightness/contrast, outside Poser, can make a huge difference to the printing. A printed image cannot show the brightness range you computer screen can.