求大神解决Itext输出pdf时候边距的问题

OutputStream os = response.getOutputStream();
DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();   
Document doc = builder.parse(new ByteArrayInputStream(htmlStr.getBytes("utf-8")));     
ITextRenderer renderer = new ITextRenderer(); 
ITextFontResolver fontResolver = renderer.getFontResolver();  
renderer.setDocument(doc, null); 
fontResolver.addFont("C:/Windows/Fonts/SIMSUN.TTC",BaseFont.IDENTITY_H, BaseFont.NOT_EMBEDDED);
renderer.layout();
renderer.createPDF(os);
os.close();
代码在上面,因为我要设置边距,但是renderer.createPDF(os)这句代码里面已经默认设置了,我想问问各位有没有办法解决,不是要new Document(new Rectangle(PageSize.A4),50,50,50,50)这种解决方法.
谢谢各位~~

补充：Java ,  Java相关