Protect PDF Files in Java

Aspose.PDF for Java provides several APIs for securing PDF files with passwords and permissions.

Protect PDF documents in Java

The examples in ProtectDocumentExamples.java demonstrate how to:

1. Apply encryption to a Document with user and owner passwords.
2. Restrict permissions with DocumentPrivilege.
3. Choose a CryptoAlgorithm for the protected Document.
4. Decrypt a protected Document.
5. Change existing passwords on the Document.
6. Test candidate passwords with PdfFileInfo and Document.

Encrypt a PDF with restricted privileges

public static void encryptPassword(Path inputFile, Path outputFile) {
    Document document = new Document(inputFile.toString());
    try {
        DocumentPrivilege documentPrivilege = DocumentPrivilege.getForbidAll();
        documentPrivilege.setAllowScreenReaders(true);

        document.encrypt(
                USER_PASSWORD,
                OWNER_PASSWORD,
                documentPrivilege,
                CryptoAlgorithm.AESx128,
                false);
        document.save(outputFile.toString());
    } finally {
        document.close();
    }
}

Encrypt a PDF file

public static void encryptPdfFile(Path inputFile, Path outputFile) {
    Document document = new Document(inputFile.toString());
    try {
        document.encrypt(
                USER_PASSWORD,
                OWNER_PASSWORD,
                DocumentPrivilege.getAllowAll(),
                CryptoAlgorithm.RC4x128,
                false);
        document.save(outputFile.toString());
    } finally {
        document.close();
    }
}

Decrypt a protected PDF

public static void decryptPdfFile(Path inputFile, Path outputFile) {
    Document document = new Document(inputFile.toString(), USER_PASSWORD);
    try {
        document.decrypt();
        document.save(outputFile.toString());
    } finally {
        document.close();
    }
}

Change passwords

public static void changePassword(Path inputFile, Path outputFile) {
    Document document = new Document(inputFile.toString(), OWNER_PASSWORD);
    try {
        document.changePasswords(OWNER_PASSWORD, "newuser", "newowner");
        document.save(outputFile.toString());
    } finally {
        document.close();
    }
}

Determine the correct password from a list

public static void determineCorrectPasswordFromList(Path inputFile) {
    try (PdfFileInfo info = new PdfFileInfo(inputFile.toString())) {
        System.out.println("File is password protected: " + info.isEncrypted());
    }
    String[] passwords = {"test", "test1", "test2", "test3", USER_PASSWORD};
    for (String password : passwords) {
        try {
            Document document = new Document(inputFile.toString(), password);
            try {
                int pageCount = document.getPages().size();
                if (pageCount > 0) {
                    System.out.println("Password '" + password + "' is correct. Pages: " + pageCount);
                }
            } finally {
                document.close();
            }
        } catch (InvalidPasswordException ex) {
            System.out.println("Wrong password: " + password);
        }
    }
}