Added advanced example on how to use page slots

Source/QuestPDF.Examples/PageBackgroundForegroundExample.cs

@@ -53,5 +53,58 @@ namespace QuestPDF.Examples
                     });
                 });
         }
+
+        [Test]
+        public void CustomContentOnPageSides()
+        {
+            RenderingTest
+                .Create()
+                .ProduceImages()
+                .MaxPages(100)
+                .ShowResults()
+                .RenderDocument(document =>
+                {
+                    document.Page(page =>
+                    {
+                        const float horizontalMargin = 1.5f;
+                        const float verticalMargin = 1f;
+                        
+                        page.Size(PageSizes.A4);
+                        page.MarginVertical(verticalMargin, Unit.Inch);
+                        page.MarginHorizontal(horizontalMargin, Unit.Inch);
+                        page.PageColor(Colors.White);
+
+                        page.Background()
+                            .PaddingVertical(verticalMargin, Unit.Inch)
+                            .RotateRight()
+                            .Decoration(decoration =>
+                            {
+                                decoration.Before().RotateRight().RotateRight().Element(DrawSide);
+                                decoration.Content().Extend();
+                                decoration.After().Element(DrawSide);
+
+                                void DrawSide(IContainer container)
+                                {
+                                    container
+                                        .Height(horizontalMargin, Unit.Inch)
+                                        .AlignMiddle()
+                                        .Row(row =>
+                                        {   
+                                            row.AutoItem().PaddingRight(16).Text("COMPANY NAME").FontSize(16).FontColor(Colors.Red.Medium);
+                                            row.RelativeItem().PaddingTop(12).ExtendHorizontal().LineHorizontal(2).LineColor(Colors.Red.Medium);
+                                        });
+                                }
+                            });
+                        
+                        page.Content().Column(column =>
+                        {
+                            column.Spacing(25);
+
+                            foreach (var i in Enumerable.Range(1, 100))
+                                column.Item().Background(Colors.Grey.Lighten2).Height(75).AlignCenter().AlignMiddle().Text(i.ToString()).FontSize(16);
+                        });
+                    });
+                });
+        }
     }
 }