// For complete examples and data files, please go to https://github.com/groupdocs-viewer/GroupDocs.Viewer-for-Java
// Setup GroupDocs.Viewer config
ViewerConfig config = Utilities.getConfiguration();
// Create html handler
ViewerImageHandler imageHandler = new ViewerImageHandler(config);
String guid = fileName;
// Set OnePagePerSheet = false to render multiple pages per sheet. By default OnePagePerSheet = true.
ImageOptions imageOptions = new ImageOptions();
imageOptions.getCellsOptions().setOnePagePerSheet(false);
//Get pages
List<PageImage> pages = imageHandler.getPages(guid, imageOptions);
for (PageImage page : pages) {
Utilities.saveAsImage(page.getPageNumber() + "_" + fileName, "png", page.getStream());
}