One more word:
As you see here in the "pdfReport.php"
Code:
private function _getCss()
{
$oTemplate = \Template::model()->getInstance(null, $this->_iSurveyId);
if (is_file($oTemplate->filesPath.'pdfreport.css')) {
/* @todo : get parent */
return file_get_contents($oTemplate->filesPath.'/pdfreport.css');
}
return file_get_contents(dirname(__FILE__).'/pdfreport.css');
}
the css is taken per default from the plugin's pdfreport.css
But as it is always preferable to design the report similar to the theme you can use the folder of the theme (what I prefer).
And since this report is based on TCPDF resp. mPDF, you should read the documentation there and study some examples of TCPDF.
Furthermore you might get help in the "pdf.php" (in "application/libraries/admin")
And as Denis said, try to use "limeMpdf". But I am not fasmiliar with it.
Joffm