for( XSLFShape shape : slide[i].getShapes() ){
     if ( shape instanceof XSLFTextShape ){
      XSLFTextShape txtshape = (XSLFTextShape)shape ;
      System.out.println("txtshape" + (i+1) + ":" + txtshape.getShapeName());
      System.out.println("text:" +txtshape.getText());
       
      for ( XSLFTextParagraph textPara : txtshape.getTextParagraphs() ){
       List<XSLFTextRun> textRunList = textPara.getTextRuns();
       for(XSLFTextRun textRun: textRunList) {
        textRun.setFontFamily("宋体");
       }
      }
     }
    }

public static void convertPPTToPDF(String sourcepath, String destinationPath, String fileType) throws Exception {
  FileInputStream inputStream = new FileInputStream(sourcepath);
  double zoom = 2;
  AffineTransform at = new AffineTransform();
  at.setToScale(zoom, zoom);
  Document pdfDocument = new Document();
  PdfWriter pdfWriter = PdfWriter.getInstance(pdfDocument, new FileOutputStream(destinationPath));
  PdfPTable table = new PdfPTable(1);
  pdfWriter.open();
  pdfDocument.open();
  Dimension pgsize = null;
  Image slideImage = null;
  BufferedImage img = null;
  if (fileType.equalsIgnoreCase(".ppt")) {
   SlideShow ppt = new SlideShow(inputStream);
   inputStream.close();
   pgsize = ppt.getPageSize();
   Slide slide[] = ppt.getSlides();
   pdfDocument.setPageSize(new Rectangle((float) pgsize.getWidth(), (float) pgsize.getHeight()));
   pdfWriter.open();
   pdfDocument.open();
   for (int i = 0; i < slide.length; i++) {
     
    TextRun[] truns = slide[i].getTextRuns();  
    for ( int k=0;k<truns.length;k++){  
     RichTextRun[] rtruns = truns[k].getRichTextRuns();  
     for(int l=0;l<rtruns.length;l++){  
//      int index = rtruns[l].getFontIndex();  
//      String name = rtruns[l].getFontName();    
      rtruns[l].setFontIndex(1);  
      rtruns[l].setFontName("宋体");       
     }  
    }  
     
     
    img = new BufferedImage((int) Math.ceil(pgsize.width * zoom), (int) Math.ceil(pgsize.height * zoom), BufferedImage.TYPE_INT_RGB);
    Graphics2D graphics = img.createGraphics();
    graphics.setTransform(at);
 
    graphics.setPaint(Color.white);
    graphics.fill(new Rectangle2D.Float(0, 0, pgsize.width, pgsize.height));
    slide[i].draw(graphics);
    graphics.getPaint();
    slideImage = Image.getInstance(img, null);
    table.addCell(new PdfPCell(slideImage, true));
   }
  }
  if (fileType.equalsIgnoreCase(".pptx")) {
   XMLSlideShow ppt = new XMLSlideShow(inputStream);
   pgsize = ppt.getPageSize();
   XSLFSlide slide[] = ppt.getSlides();
   pdfDocument.setPageSize(new Rectangle((float) pgsize.getWidth(), (float) pgsize.getHeight()));
   pdfWriter.open();
   pdfDocument.open();
    
    
   for (int i = 0; i < slide.length; i++) {
    for( XSLFShape shape : slide[i].getShapes() ){
     if ( shape instanceof XSLFTextShape ){
      XSLFTextShape txtshape = (XSLFTextShape)shape ;
      // System.out.println("txtshape" + (i+1) + ":" + txtshape.getShapeName());
      //System.out.println("text:" +txtshape.getText());
       
      for ( XSLFTextParagraph textPara : txtshape.getTextParagraphs() ){
       List<XSLFTextRun> textRunList = textPara.getTextRuns();
       for(XSLFTextRun textRun: textRunList) {
        textRun.setFontFamily("宋体");
       }
      }
     }
    }
    img = new BufferedImage((int) Math.ceil(pgsize.width * zoom), (int) Math.ceil(pgsize.height * zoom), BufferedImage.TYPE_INT_RGB);
    Graphics2D graphics = img.createGraphics();
    graphics.setTransform(at);
    graphics.setPaint(Color.white);
    graphics.fill(new Rectangle2D.Float(0, 0, pgsize.width, pgsize.height));
    slide[i].draw(graphics);
     
     
//    FileOutputStream out = new FileOutputStream("src/main/resources/test"+i+".jpg"); 
//    javax.imageio.ImageIO.write(img, "jpg", out);
     
     
     
    graphics.getPaint();
    slideImage = Image.getInstance(img, null);
    table.addCell(new PdfPCell(slideImage, true));
   }
  }
  pdfDocument.add(table);
  pdfDocument.close();
  pdfWriter.close();
  System.out.println("Powerpoint file converted to PDF successfully");
 }

<dependency>
  <groupId>org.apache.poi</groupId>
  <artifactId>poi</artifactId>
 <!-- <version>3.13</version> -->
  <version>3.9</version>
 </dependency>
 <dependency>
  <groupId>org.apache.poi</groupId>
  <artifactId>poi-ooxml</artifactId>
  <!-- <version>3.10-FINAL</version> -->
  <version>3.9</version>
 </dependency>
  
 <dependency>
   <groupId>com.itextpdf</groupId>
   <artifactId>itextpdf</artifactId>
   <version>5.5.7</version>
 </dependency>
 
 <dependency>
  <groupId>com.itextpdf.tool</groupId>
  <artifactId>xmlworker</artifactId>
  <version>5.5.7</version>
 </dependency>
 <dependency>
  <groupId>org.apache.poi</groupId>
  <artifactId>poi-scratchpad</artifactId>
  <!-- <version>3.12</version> -->
  <version>3.9</version>
 </dependency>