exec("inkscape -A ".$target_pdf." ".$source_svg." -T -a 0:0:".$svgWidth.":".$svgHeight);
$target_pdf - a full path to the PDF file to be stored;
$source_svg - a full path to the source Design SVG obtained from LiveArt;
$svgWidth, $svgHeight - a viewport measurements you'd like to render. Typically correspond to pixels dimensions of canvas area.