我對(duì) pdfBox API 有疑問。我正在嘗試使用以下代碼加密合并的 pdfdocument：這是合并/創(chuàng)建文檔的功能    public static void fillMultipleReportsInOne(List<report> reports) throws IOException {        PDFMergerUtility PDFmerger = new PDFMergerUtility();         PDDocument resultPDF = new PDDocument();        for (report report : reports) {            try             {                PDDocument pdfDocument = PDDocument.load(new File(SRC + "test.pdf"));                // get the document catalog                PDAcroForm acroForm = pdfDocument.getDocumentCatalog().getAcroForm();                // as there might not be an AcroForm entry a null check is necessary                setFormFields(acroForm, report.getName(), report.getArea(), report.getOperatingActivities(), report.getVocationlaSchool(), report.getWeeklyTopics());                // Save and close the filled out form.                PDFmerger.appendDocument(resultPDF, pdfDocument);        } catch (Exception e) {            e.printStackTrace();        }    }    encryptPDF(resultPDF, SRC + "merged.pdf");}這是加密的功能： public static PDDocument encryptPDF(PDDocument pddocumentToEncrypt, String SRC) {        // Define the length of the encryption key.        // Possible values are 40 or 128 (256 will be available in PDFBox 2.0).        int keyLength = 128;        AccessPermission ap = new AccessPermission();        // Disable printing, everything else is allowed        ap.setCanModifyAnnotations(false);        ap.setCanFillInForm(false);        ap.setCanModify(false);        // Owner password (to open the file with all permissions) is "12345"        // User password (to open the file but with restricted permissions, is empty here)         StandardProtectionPolicy spp = new StandardProtectionPolicy("12334", "", ap);        spp.setEncryptionKeyLength(keyLength);        spp.setPermissions(ap);我的結(jié)果如下所示：結(jié)果