Pimcore\Model\Asset\Document::update PHP Method

    protected function update()
    {
        $this->clearThumbnails();
        if ($this->getDataChanged()) {
            $tmpFile = $this->getTemporaryFile();
            try {
                $pageCount = $this->readPageCount($tmpFile);
                if ($pageCount !== null && $pageCount > 0) {
                    $this->setCustomSetting("document_page_count", $pageCount);
                }
            } catch (\Exception $e) {
            }
            unlink($tmpFile);
        }
        parent::update();
    }