In develop, Crop Overlay, click the double triangles to the left of the lock, either choose one of the sizes which show or click edit and make your own. This resizes your image. In print, you select the paper size in Print Setup, which is in the lower left. This opens your printer dialog box. When you get all the controls set in the print setup dialog and the LR print page, you can make a new custom template ('+' on Template Browser) which will remember your Lightroom settings. You may still have to check your printer dialog box, as mine remembers the last setting only.