H'lo, Misty!  The document (preview) window is a bit irritating in that it seems to be determined to re-dock.  The trick is where on the screen you position it.  I often drag it up to the top edge.  If the empty dock area is highlighted blue, don't let go of the mouse or the window will redock (and resize as needed to fit).  Once you have the document (preview) window floated, you can enter precise numerical dimensions.  I have, on occasion, dragged on the docked boundaries to get a window of the precise aspect ratio (1.6), but that isn't easy. 

     If you have a second monitor hooked up, I like to float & drag most/all of the tool/control windows off to the second monitor.  This leaves lots of unimpeded real estate for the preview window, and the hierarchy and library can be made the full height of the second monitor.  If you have the display mode window and the manipulation tool windows floated, try dragging the bottom edge to heighten the window, then drag the side edge to narrow it.  I would guess that the buttons would likewise reorient vertically if the docked window were dragged to a tall narrow shape, but I've never had reason to try it.

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5