Example:

Document doc = new Document(getMyDir() + "Rendering.docx");

// Saving a document to PDF, to an image, or printing for the first time will automatically
// cache the layout of the document within its pages.
doc.save(getArtifactsDir() + "Document.UpdatePageLayout.1.pdf");

// Modify the document in some way.
doc.getStyles().get("Normal").getFont().setSize(6.0);
doc.getSections().get(0).getPageSetup().setOrientation(Orientation.LANDSCAPE);
doc.getSections().get(0).getPageSetup().setMargins(Margins.MIRRORED);

// In the current version of Aspose.Words, modifying the document does not automatically rebuild 
// the cached page layout. If we wish for the cached layout
// to stay up to date, we will need to update it manually.
doc.updatePageLayout();

doc.save(getArtifactsDir() + "Document.UpdatePageLayout.2.pdf");