[fw-general] Zend PDF setAlpha undefined method?

[Charlie Dover]

How does one use setAlpha correctly? Using zend 1.102 and setAplha  
ALWAYS fails with 'Call to undefined method Zend_Pdf_Page::setAlpha()'.

very basic code:
$pdf = new Zend_Pdf();
$pdf->pages[] = ($page1 = $pdf->newPage('letter-landscape'));
$font = Zend_Pdf_Font::fontWithName(Zend_Pdf_Font::FONT_HELVETICA);
$page1->setFont($font, 16);
$page1->drawText('Hello', 72, 72);

$page1->setAlpha(0.5); // this always fails

// remaining code removed


TIA

sorry if this got posted twice