Apache PDFBox is open source Java library for working with PDF files. This library allows processing on PDF files in many ways. I am using this for converting PDF files to images. I used its version 2.

Following is code for PDF to image conversion. This code is converting pdf pages to images and save them to another directory.

import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.File;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.ImageType;
import org.apache.pdfbox.rendering.PDFRenderer;
import org.apache.pdfbox.tools.imageio.ImageIOUtil;

public class PdfToImage {

	public static void main(String[] args) throws IOException {
		String pdfFilename = "resources/pdfs/file-name.pdf";
		String imagesDir = "resources/pdfImg/images/";
		PDDocument document = PDDocument.load(new File(pdfFilename));
		PDFRenderer pdfRenderer = new PDFRenderer(document);
		File destinationFile = new File(imagesDir);
		for (int page = 0; page < document.getNumberOfPages(); ++page)
		{ 
		    BufferedImage bim = pdfRenderer.renderImageWithDPI(page, 300, ImageType.RGB);
		    ImageIOUtil.writeImage(bim, destinationFile + "-" + (page+1) + ".png", 300);
		}
		document.close();
	}

	
}

Change pdfFilename and imagesDir variable values as per your requirements.