public function getPageCount()
    {
        if ($this->pageCount === null) {
            $catalog = $this->parser->getCatalog();

            $pages = PdfType::resolve(PdfDictionary::get($catalog, 'Pages'), $this->parser);
            $count = PdfType::resolve(PdfDictionary::get($pages, 'Count'), $this->parser);

            $this->pageCount = PdfNumeric::ensure($count)->value;
        }

        return $this->pageCount;
    }