Add a comment explaning necessity of page removal during #relayout

Author: Snipx

layout/src/main/java/com/itextpdf/layout/Document.java

@@ -193,6 +193,10 @@ public void relayout() {
             nextRelayoutRenderer = new DocumentRenderer(this, immediateFlush);
         }
 
+        // Even though #relayout() only makes sense when immediateFlush=false and therefore no elements
+        // should have been written to document, still empty pages are created during layout process
+        // because we need to know the effective page size which may differ from page to page.
+        // Therefore, we remove all the pages that might have been created before proceeding to relayout elements.
         while (pdfDocument.getNumberOfPages() > 0) {
             pdfDocument.removePage(pdfDocument.getNumberOfPages());
         }

layout/src/main/java/com/itextpdf/layout/renderer/DocumentRenderer.java

@@ -195,7 +195,7 @@ protected PageSize addNewPage(PageSize customPageSize) {
     }
 
     /**
-     * Ensures that PDF document has n pages. If document has less pages,
+     * Ensures that PDF document has n pages. If document has fewer pages,
      * adds new pages by calling {@link #addNewPage(PageSize)} method.
      *
      * @param n the expected number of pages if document