// Save new PDF note.
    echo $pdfHandler->savePDFNote($_GET['page'], $_GET['top'], $_GET['left']);
} elseif (isset($_POST['savepdfmarkers']) && !empty($_POST['page']) && !empty($_POST['markers'])) {
    // Save PDF markers.
    echo $pdfHandler->savePDFMarkers($_POST['page'], $_POST['markers']);
} elseif (isset($_GET['getpdfmarkers'])) {
    $users = null;
    if (isset($_GET['users']) && $_GET['users'] === 'other') {
        $users = 'other';
    }
    // Get PDF markers.
    echo $pdfHandler->getPDFMarkers($users);
} elseif (isset($_GET['getpdfnotes'])) {
    $users = null;
    if (isset($_GET['users']) && $_GET['users'] === 'other') {
        $users = 'other';
    }
    // Get PDF markers.
    echo $pdfHandler->getPDFNotes($users);
} elseif (isset($_GET['downloadpdf'])) {
    $mode = null;
    $attachments = array();
    if (isset($_GET['mode']) && $_GET['mode'] === 'download') {
        $mode = 'download';
    }
    if (isset($_GET['attachments'])) {
        $attachments = $_GET['attachments'];
    }
    // Download PDF.
    $pdfHandler->downloadPDF($mode, $attachments);
}