public void removeUsageRights() {
        PdfDictionary perms = catalog.getAsDict(PdfName.PERMS);
        if (perms == null)
            return;
        perms.remove(PdfName.UR);
        perms.remove(PdfName.UR3);
        if (perms.size() == 0)
            catalog.remove(PdfName.PERMS);
    }