Java API，用于加密/解密pdf文件

使用iText：

  // Assuming you provide the following yourself:  File inputFile;   File outputFile;  String userPassword;  String ownerPassword;  // A bit-field containing file permissions.  int permissions = PDFWriter.ALLOW_PRINTING | PDFWriter.ALLOW_COPY;  PdfReader reader = new PdfReader(inputFile);  PdfEncryptor.encrypt(reader, new FileOutputStream(outputFile),      ENCRYPTION_AES128, userPassword, ownerPassword,       permissions);

这是PDFEncryptor和PDFWriter的API
（用于权限）。