您可以通过解析布局元素而不是直接对文件或pdfDocument进行分析，并使用页面事件应用页面大小修改。
我做了一个简单的例子如下切换方向每隔X页：
public void createPdfFromHtml(String htmlSource, String pdfDest, String resoureLoc) throws IOException, InterruptedException {
File pdf = new File(pdfDest);
pdf.getParentFile().mkdirs();
//convertToElements takes the string containing the HTML as input
byte[] bytes = StreamUtil.inputStreamToArray(new FileInputStream(htmlSource));
String html = new String(bytes);
PdfWriter writer = new PdfWriter(pdfDest);
PdfDocument pdfDoc = new PdfDocument(writer);
Document doc = new Document(pdfDoc,pageSize);
// Create the page size modifying event handler
PageSize pageSize = PageSize.A4;
pageSize = pageSize.rotate();//Start in landscape
int differentPageSizeInterval = 5;
PageSizeModifier pageSizeModifier = new PageSizeModifier(doc, differentPageSizeInterval, pageSize);
//Register it to the pdfDocument and set it to trigger at the start of a page
pdfDoc.addEventHandler(PdfDocumentEvent.START_PAGE,pageSizeModifier);
ConverterProperties converterProperties = new ConverterProperties();
converterProperties.setBaseUri(resoureLoc);
//Convert the html to elements
try {
//parse and return the top level elements of the <body>
List<IElement> elements = HtmlConverter.convertToElements(html, converterProperties);
for (IElement ele : elements) {
//Add the elements to the layout document
doc.add((BlockElement) ele);
}
doc.close();
} catch (PdfException e) {
System.out.println(e);
e.printStackTrace();
}
}
protected class PageSizeModifier implements IEventHandler {
Document doc;
int interval;
int counter;
PageSize pageSize;
public PageSizeModifier(Document doc, int interval,PageSize pageSize) {
this.doc = doc; //A reference to the layout document must be kept so we can change the margins on the fly
this.interval = interval;
this.counter = 1;
this.pageSize = pageSize;//Start out in landscape
}
@Override
public void handleEvent(Event event) {
if(counter == interval){
//Rotate
pageSize = pageSize.rotate();
//For the rendering framework, change the default page size
doc.getPdfDocument().setDefaultPageSize(pageSize);
//because the page was already created, we need to update the various boxes determining the pagesize
//By default, only the trim and mediabox will be present
((PdfDocumentEvent) event).getPage().setMediaBox(pageSize);
((PdfDocumentEvent) event).getPage().setTrimBox(pageSize);
//Reset the counter
counter = 1;
}else{
counter++;
}
}