<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</artifactId>
        <version>10.10.7</version>
    </dependency>
</dependencies>
    

import com.spire.pdf.PdfDocument;
import com.spire.pdf.PdfPageBase;
import com.spire.pdf.graphics.PdfImage;

import java.awt.*;
import java.io.File;

public class ConvertMultipleImagesIntoPdf {

    public static void main(String[] args) {

        //Create a PdfDocument object
        PdfDocument doc = new PdfDocument();

        //Set the page margins to 0
        doc.getPageSettings().setMargins(0);

        //Get the folder where the images are stored
        File folder = new File("C:/Users/Administrator/Desktop/Images");

        //Iterate through the files in the folder
        for (File file : folder.listFiles())
        {
            //Load a particular image
            PdfImage pdfImage = PdfImage.fromFile(file.getPath());

            //Get the image width and height
            int width = pdfImage.getWidth();
            int height = pdfImage.getHeight();

            //Add a page that has the same size as the image
            PdfPageBase page = doc.getPages().add(new Dimension(width, height));

            //Draw image at (0, 0) of the page
            page.getCanvas().drawImage(pdfImage, 0, 0, width, height);
        }

        //Save to file
        doc.saveToFile("CombineImagesToPdf.pdf");
        doc.dispose();
    }
}

<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</artifactId>
        <version>10.10.7</version>
    </dependency>
</dependencies>
    

import com.spire.pdf.PdfDocument;
import com.spire.pdf.graphics.PdfImageType;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

public class ConvertPdfToJpeg {

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

        //Create a PdfDocument instance
        PdfDocument pdf = new PdfDocument();

        //Load a sample PDF document
        pdf.loadFromFile("C:\\Users\\Administrator\\Desktop\\Input.pdf");

        //Loop through the pages
        for (int i = 0; i < pdf.getPages().getCount(); i++) {

            //Save the current page as a buffered image
            BufferedImage image = pdf.saveAsImage(i, PdfImageType.Bitmap, 300, 300);

            //Re-create a buffered image in RGB type
            BufferedImage newImg = new BufferedImage(image.getWidth(), image.getHeight(), BufferedImage.TYPE_INT_RGB);
            newImg.getGraphics().drawImage(image, 0, 0, null);

            //Write the image data as a .jpg file
            File file = new File("C:\\Users\\Administrator\\Desktop\\Output\\" + String.format(("ToImage-%d.jpg"), i));
            ImageIO.write(newImg, "JPEG", file);
        }
        pdf.close();
    }
}

import com.spire.pdf.*;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

public class ConvertPdfToPng {

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

        //Create a PdfDocument object
        PdfDocument doc = new PdfDocument();

        //Load a sample PDF document
        doc.loadFromFile("C:\\Users\\Administrator\\Desktop\\Input.pdf");

        //Make the background of the generated PNG files transparent 
        //doc.getConvertOptions().setPdfToImageOptions(0);

        //Loop through the pages
        for (int i = 0; i < doc.getPages().getCount(); i++) {

            //Save the current page as a buffered image
            BufferedImage image = doc.saveAsImage(i);

            //Write the image data as a .png file
            File file = new File("C:\\Users\\Administrator\\Desktop\\Output\\" + String.format("ToImage-%d.png", i));
            ImageIO.write(image, "png", file);
        }
        doc.close();
    }
}

doc.getConvertOptions().setPdfToImageOptions(0);