1600 x 900 exceeds the minimum requirements. I've temporarily changed my screen resolution to 1600 x 900 and the PDF Options window fits easily. At that resolution, I can get the bottom of the window to be cut off if the GUI scaling in OpenOffice is set above 120% and Windows is set to enlarge objects in the display.
The setting in OpenOffice is at Tools > Options > OpenOffice > View. The setting in Windows 8.1 is at Control Panel > Appearance and Personalization > Display.