diff --git a/src/config/paperSizes.ts b/src/config/paperSizes.ts
new file mode 100644
index 0000000..cc3e384
--- /dev/null
+++ b/src/config/paperSizes.ts
@@ -0,0 +1,15 @@
+/**
+ * ابعاد استاندارد کاغذ (ISO A) به پیکسل - همان مقیاس ادیتور (A4 = 794×1123)
+ */
+export const PAPER_DIMENSIONS = {
+  a3: { width: 1123, height: 1587 },
+  a4: { width: 794, height: 1123 },
+  a5: { width: 561, height: 794 },
+} as const;
+
+export type PaperSizeKey = keyof typeof PAPER_DIMENSIONS;
+
+export function getPaperDimensions(size: string): { width: number; height: number } {
+  const key = size?.toLowerCase() as PaperSizeKey;
+  return PAPER_DIMENSIONS[key] ?? PAPER_DIMENSIONS.a4;
+}
diff --git a/src/pages/editor/Editor.tsx b/src/pages/editor/Editor.tsx
index 597a50d..b451175 100644
--- a/src/pages/editor/Editor.tsx
+++ b/src/pages/editor/Editor.tsx
@@ -45,7 +45,7 @@ const Editor: FC = () => {
             isLayersPanelOpen ? "xl:pl-[296px]" : "xl:pl-[80px]"
         )}>
             <LayersPanel isOpen={isLayersPanelOpen} setIsOpen={setIsLayersPanelOpen} />
-            <EditorCanvas />
+            <EditorCanvas catalogSize={data?.data?.size} />
             <EditorSidebar />
         </div>
     )
diff --git a/src/pages/editor/components/EditorCanvas.tsx b/src/pages/editor/components/EditorCanvas.tsx
index 093e16d..cc73b4a 100644
--- a/src/pages/editor/components/EditorCanvas.tsx
+++ b/src/pages/editor/components/EditorCanvas.tsx
@@ -13,7 +13,11 @@ import ObjectsLayer from "./canvas/ObjectsLayer";
 import CellEditor from "@/components/CellEditor";
 import ZoomControls from "./ZoomControls";
 
-const EditorCanvas = () => {
+type EditorCanvasProps = {
+  catalogSize?: string;
+};
+
+const EditorCanvas = ({ catalogSize }: EditorCanvasProps) => {
   const stageRef = useRef<Konva.Stage>(null);
   const layerRef = useRef<Konva.Layer>(null);
 
@@ -30,7 +34,7 @@ const EditorCanvas = () => {
   } = useEditorStore();
 
   const { transformerRef, handleStageMouseDown, handleStageMouseMove, handleStageMouseUp } = useDrawingHandlers();
-  const stageSize = useStageSize();
+  const stageSize = useStageSize(catalogSize);
   useKeyboardMovement();
 
   const { handleSelect, handleCellClick, handleCellDblClick } = useSelectionHandlers();
diff --git a/src/pages/editor/components/canvas/useStageSize.ts b/src/pages/editor/components/canvas/useStageSize.ts
index d5357d3..8db606f 100644
--- a/src/pages/editor/components/canvas/useStageSize.ts
+++ b/src/pages/editor/components/canvas/useStageSize.ts
@@ -1,35 +1,33 @@
 import { useState, useEffect } from "react";
+import { getPaperDimensions } from "@/config/paperSizes";
 
-export const A4_WIDTH = 794;
-export const A4_HEIGHT = 1123;
 const SCALE = 0.8;
 
-export const useStageSize = () => {
+export const useStageSize = (catalogSize?: string) => {
+    const { width: baseWidth, height: baseHeight } = getPaperDimensions(catalogSize ?? "a4");
+
     const [stageSize, setStageSize] = useState({
-        width: A4_WIDTH,
-        height: A4_HEIGHT,
+        width: baseWidth,
+        height: baseHeight,
         scale: SCALE,
     });
 
     useEffect(() => {
+        const { width, height } = getPaperDimensions(catalogSize ?? "a4");
+
         const handleResize = () => {
             const maxWidth = window.innerWidth - 400;
             const maxHeight = window.innerHeight - 100;
-            const scaleX = maxWidth / A4_WIDTH;
-            const scaleY = maxHeight / A4_HEIGHT;
+            const scaleX = maxWidth / width;
+            const scaleY = maxHeight / height;
             const newScale = Math.min(scaleX, scaleY, SCALE);
-
-            setStageSize({
-                width: A4_WIDTH,
-                height: A4_HEIGHT,
-                scale: newScale,
-            });
+            setStageSize({ width, height, scale: newScale });
         };
 
         handleResize();
         window.addEventListener("resize", handleResize);
         return () => window.removeEventListener("resize", handleResize);
-    }, []);
+    }, [catalogSize]);
 
     return stageSize;
 };
diff --git a/src/pages/viewer/Viewer.tsx b/src/pages/viewer/Viewer.tsx
index b3b17c9..7bee578 100644
--- a/src/pages/viewer/Viewer.tsx
+++ b/src/pages/viewer/Viewer.tsx
@@ -58,7 +58,7 @@ const Viewer: FC = () => {
 
     return (
         <div className="w-full h-full">
-            <BookViewer pages={pages} />
+            <BookViewer pages={pages} catalogSize={data?.data?.size} />
         </div>
     );
 };
diff --git a/src/pages/viewer/components/BookPage.tsx b/src/pages/viewer/components/BookPage.tsx
index bb56305..e7d55d3 100644
--- a/src/pages/viewer/components/BookPage.tsx
+++ b/src/pages/viewer/components/BookPage.tsx
@@ -5,6 +5,8 @@ import type { EditorObject } from '@/pages/editor/store/editorStore';
 type BookPageProps = {
   page: PageData;
   scale?: number;
+  pageWidth?: number;
+  pageHeight?: number;
   onLinkClick?: (linkUrl: string) => void;
 };
 
@@ -15,7 +17,8 @@ type BookPageProps = {
  * این کامپوننت به عنوان child برای HTMLFlipBook استفاده می‌شود
  * نیاز به forwardRef دارد تا react-pageflip بتواند ref را مدیریت کند
  */
-const BookPage = forwardRef<HTMLDivElement, BookPageProps>(({ page, scale = 1, onLinkClick }, ref) => {
+const BookPage = forwardRef<HTMLDivElement, BookPageProps>(
+  ({ page, scale = 1, pageWidth, pageHeight, onLinkClick }, ref) => {
   // تابع برای تبدیل opacity به رنگ (مثل editor)
   // در editor، getColorWithOpacity انتظار opacity 0-100 دارد
   // در dataTransformer، opacity از 0-1 به 0-100 تبدیل شده است
@@ -462,6 +465,9 @@ const BookPage = forwardRef<HTMLDivElement, BookPageProps>(({ page, scale = 1, o
     }
   };
 
+  const width = pageWidth ?? 794 * scale;
+  const height = pageHeight ?? 1123 * scale;
+
   return (
     <div
       ref={ref}
@@ -472,8 +478,8 @@ const BookPage = forwardRef<HTMLDivElement, BookPageProps>(({ page, scale = 1, o
         backgroundColor: '#ffffff',
         overflow: 'hidden',
         boxSizing: 'border-box',
-        width: `${794 * scale}px`,
-        height: `${1123 * scale}px`,
+        width: `${width}px`,
+        height: `${height}px`,
         isolation: 'isolate',
         zIndex: 1,
       }}
diff --git a/src/pages/viewer/components/BookViewer.tsx b/src/pages/viewer/components/BookViewer.tsx
index d438e4e..d7d8f3b 100644
--- a/src/pages/viewer/components/BookViewer.tsx
+++ b/src/pages/viewer/components/BookViewer.tsx
@@ -1,11 +1,18 @@
-import { type FC, useRef, useCallback, useState, useEffect } from 'react';
+import { type FC, useRef, useCallback, useState, useEffect, useMemo } from 'react';
 import HTMLFlipBook from 'react-pageflip';
 import { type PageData } from '../types';
 import BookPage from './BookPage';
 import { ArrowLeft2, ArrowRight2 } from 'iconsax-react';
+import { getPaperDimensions } from '@/config/paperSizes';
 
-type BookViewerProps = {
+const VIEWER_SCALE = 0.5;
+
+// سایز کتاب همیشه A4 است (ثابت)
+const BOOK_PAPER_SIZE = 'a4';
+
+export type BookViewerProps = {
     pages: PageData[];
+    catalogSize?: string;
 };
 
 interface PageFlipAPI {
@@ -27,10 +34,24 @@ interface FlipEvent {
  * این کامپوننت از HTMLFlipBook استفاده می‌کند که یک wrapper برای PageFlip است
  * از HTML برای رندر صفحات استفاده می‌شود (نه Canvas) برای سازگاری با Konva در آینده
  */
-const BookViewer: FC<BookViewerProps> = ({ pages }) => {
+const BookViewer: FC<BookViewerProps> = ({ pages, catalogSize }) => {
     const bookRef = useRef<FlipBookInstance | null>(null);
     const [currentPage, setCurrentPage] = useState(0);
 
+    // سایز کتاب ثابت (همیشه A4)
+    const { width: bookWidth, height: bookHeight } = useMemo(
+        () => getPaperDimensions(BOOK_PAPER_SIZE),
+        []
+    );
+    const displayWidth = Math.round(bookWidth * VIEWER_SCALE);
+    const displayHeight = Math.round(bookHeight * VIEWER_SCALE);
+
+    // نسبت محتوا بر اساس catalogSize (A3/A4/A5)
+    const contentScale = useMemo(() => {
+        const { width: contentWidth } = getPaperDimensions(catalogSize ?? 'a4');
+        return VIEWER_SCALE * (bookWidth / contentWidth);
+    }, [catalogSize]);
+
     // اطمینان از اینکه currentPage همیشه در محدوده معتبر است
     useEffect(() => {
         if (currentPage < 0) {
@@ -156,13 +177,13 @@ const BookViewer: FC<BookViewerProps> = ({ pages }) => {
                 <div style={{ overflow: 'hidden', isolation: 'isolate' }}>
                     <HTMLFlipBook
                         ref={bookRef}
-                        width={397}
-                        height={561}
+                        width={displayWidth}
+                        height={displayHeight}
                         size="fixed"
-                        minWidth={397}
-                        minHeight={561}
-                        maxWidth={397}
-                        maxHeight={561}
+                        minWidth={displayWidth}
+                        minHeight={displayHeight}
+                        maxWidth={displayWidth}
+                        maxHeight={displayHeight}
                         drawShadow={true}
                         flippingTime={800}
                         usePortrait={false}
@@ -184,7 +205,14 @@ const BookViewer: FC<BookViewerProps> = ({ pages }) => {
                         onFlip={handlePageFlip}
                     >
                         {pages.map((page) => (
-                            <BookPage key={page.id} page={page} scale={0.5} onLinkClick={handleLinkClick} />
+                            <BookPage
+                                key={page.id}
+                                page={page}
+                                scale={contentScale}
+                                pageWidth={displayWidth}
+                                pageHeight={displayHeight}
+                                onLinkClick={handleLinkClick}
+                            />
                         ))}
                     </HTMLFlipBook>
                 </div>