MacOS – How to change the shape default in Preview app

In Mountain Lion, at least, there's a Opening for the first time entry in the PDF pane in Preferences, where you can select Single Page. This sets the default view mode for all PDF files.

If you for some reason can't get it to work, you could try this Terminal command (don't know if it will work in Lion) and restart Preview:

defaults write -app preview kPVPDFDefaultPageViewModeOption -int 1

(in ML, the value of kPVPDFDefaultPageViewModeOption changes to 1 in Preview's plist, when selecting Single Page)

You might want to check out this question: What window management options exist for OS X?

My recommendation, if you want it to be fully automatic, is to use Slate.

Slate is no longer in active development, but it still works and is highly customizable. Put this code in a .slate.js file in your home directory:

var rightHalf = slate.operation("move", {
   "x" : "screenSizeX/2+screenOriginX",
   "y" : "screenOriginY",
   "width" : "screenSizeX/2",
   "height" : "screenSizeY"
});
slate.on("windowOpened", function(event, win) {
    if (win.app().name() === "Preview") {
        win.doOperation(rightHalf);
    }
});