詳解Java如何實現加密或者解密PDF檔案

<repositories>
    <repository>
        <id>com.e-iceblue</id>
        <name>e-iceblue</name>
        <url>https://repo.e-iceblue.com/nexus/content/groups/public/</url>
    </repository>
</repositories>
<dependencies>
    <dependency>
        <groupId>e-iceblue</groupId>
        <artifactId>spire.pdf.free</artifactId>
        <version>5.1.0</version>
    </dependency>
</dependencies>

import java.util.EnumSet;

import com.spire.pdf.PdfDocument;
import com.spire.pdf.security.PdfEncryptionKeySize;
import com.spire.pdf.security.PdfPermissionsFlags;

public class EncryptPDF {

    public static void main(String[] args) {

        //建立PdfDocument範例
        PdfDocument pdf = new PdfDocument();

        //載入PDF範例檔案
        pdf.loadFromFile("sample.pdf");

        //加密檔案
        PdfEncryptionKeySize keySize = PdfEncryptionKeySize.Key_128_Bit;
        String openPassword = "123456";
        String permissionPassword = "abcdef";
        EnumSet flags = EnumSet.of(PdfPermissionsFlags.Print, PdfPermissionsFlags.Fill_Fields);
        pdf.getSecurity().encrypt(openPassword, permissionPassword, flags, keySize);

        //儲存檔案
        pdf.saveToFile("Encrypt.pdf");
        pdf.close();

    }

}

import com.spire.pdf.PdfDocument;
import com.spire.pdf.security.PdfEncryptionKeySize;
import com.spire.pdf.security.PdfPermissionsFlags;

public class DecryptPDF {

    public static void main(String[] args) throws Exception {

        //建立PdfDocument範例
        PdfDocument pdf = new PdfDocument();
        
        //載入加密檔案
        pdf.loadFromFile("Encrypt.pdf", "123456");

        //解密檔案
        pdf.getSecurity().encrypt("", "", PdfPermissionsFlags.getDefaultPermissions(), PdfEncryptionKeySize.Key_256_Bit, "abcdef");

        //儲存檔案
        pdf.saveToFile("Decrypt.pdf");
        pdf.close();
    }