pdf - com.itextpdf.kernel.PdfException：文档已关闭。无法执行动作

Question

我有以下方法将页面缩小到 50% ：

private void shrinkDocuments(List<PdfDocument> documentsToBeMerged){
    for (PdfDocument pdfDoc : documentsToBeMerged) {

        for (int p = 1; p <= pdfDoc.getNumberOfPages(); p++) {
            PdfPage page = pdfDoc.getPage(p);
            Rectangle media = page.getCropBox();
            if (media == null) {
                media = page.getMediaBox();
            }

            // Shrink the page to 50%
            Rectangle crop = new Rectangle(0, 0, media.getWidth() / 2, media.getHeight() / 2);
            page.setMediaBox(crop);
            page.setCropBox(crop);


        }

        pdfDoc.close();
    }

}

调试我看到程序抛出一个com.itextpdf.kernel.PdfException: Document was closed. It is impossible to execute action.

我该如何解决这个问题？我怎样才能再次打开这个文件？