You can use this code inside the Callback function of your save button:
[filename, pathname] = uiputfile({'*.pdf';'*.png';'*.*'},'Save as');
if isequal(filename,0) || isequal(pathname,0)
% user selected cancel button
else
% user selected a pathname and filename
% you can use these variables to save what you want
% in that path and by that name
end
you can also specify a path as default:
[filename, pathname] = uiputfile({'*.pdf';'*.png';'*.*'},'Save as', 'C:\untitle.png');
