Hi,
there are several possibilities,
either place each button individually at the bottom by align="bottom" and x/y distance values,
or create a parent image as container (can be the first button or an transparent background image), and align the other buttons via parent="parentname" and align/x/y withhin that parent container,
as example see the "buttons" and "buttonsbar" examples from the viewer download package (folder "examples\xml-usage"),
best regards,
Klaus