Использовать публичный метод page_text()
// Documentation
* @param float $x
* @param float $y
* @param string $text the text to write
* @param string $font the font file to use
* @param float $size the font size, in points
* @param array $color
* @param float $word_space word spacing adjustment
* @param float $char_space char spacing adjustment
* @param float $angle angle to write the text at, measured CW starting from the x-axis
Мой пример (https://prnt.sc/mifmxl):
$html = 'Text to test...';
$dompdf = new Dompdf();
$dompdf->loadHtml($html);
$dompdf->setPaper('A4', 'portrait');
$dompdf->render();
// Parameters
$x = 505;
$y = 790;
$text = "{PAGE_NUM} of {PAGE_COUNT}";
$font = $dompdf->getFontMetrics()->get_font('Helvetica', 'normal');
$size = 10;
$color = array(0,0,0);
$word_space = 0.0;
$char_space = 0.0;
$angle = 0.0;
$dompdf->getCanvas()->page_text(
$x, $y, $text, $font, $size, $color, $word_space, $char_space, $angle
);
// stream
$dompdf->stream('pdf_out.pdf', array('Attachment' => false));
Версия: DomPDF ( v0.8.3 )