diff -ruN a/src/IDocument.cxx b/src/IDocument.cxx
--- a/src/IDocument.cxx	2009-09-06 17:32:59.381071647 +0800
+++ b/src/IDocument.cxx	2009-09-06 17:39:38.517291109 +0800
@@ -27,10 +27,11 @@
 G_LOCK_DEFINE_STATIC (pageSearch);
 
 // Constants.
-static const gdouble ZOOM_IN_FACTOR = 1.2;
-static const gdouble ZOOM_IN_MAX = 4.0;
-static const gdouble ZOOM_OUT_FACTOR = (1.0 / ZOOM_IN_FACTOR);
-static const gdouble ZOOM_OUT_MAX = 0.05409;
+static const gint MAX_ZOOM_STEPS = 19;
+static const gdouble ZOOM_FACTORS[MAX_ZOOM_STEPS] =
+  { 0.1, 0.13, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.8,  // zoom out
+    1.0,                                            // default
+    1.25, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 8.0 }; // zoom in
 static const guint CACHE_SIZE = 3;
 
 /// This is the error domain that will be used to report Document's errors.
@@ -148,6 +149,8 @@
     m_Scale = 1.0f;
     m_Subject = NULL;
     m_Title = NULL;
+
+    m_zoomStepsPerformed = 9;
 }
 
 ///
@@ -1216,18 +1219,18 @@
 gboolean
 IDocument::canZoomIn (void)
 {
-    return ( getZoom () * ZOOM_IN_FACTOR <= ZOOM_IN_MAX );
+    return getZoom () < ZOOM_FACTORS[MAX_ZOOM_STEPS-1];
 }
 
 ///
 /// @brief Checks if is possible to zoom out.
 ///
-/// Checks if after zooming out the zoom level will be above the min level.
+/// Checks if after zooming out the zoom level will be below the min level.
 ///
 gboolean
 IDocument::canZoomOut (void)
 {
-    return ( getZoom () * ZOOM_OUT_FACTOR >= ZOOM_OUT_MAX );
+    return getZoom () > ZOOM_FACTORS[0];
 }
 
 ///
@@ -1251,8 +1254,15 @@
 {
     if ( ABS (zoom - m_Scale) > 0.00001 )
     {
+        gint idx;
+        gint lim = MAX_ZOOM_STEPS - 1;
+
         G_LOCK (JobRender);
-        m_Scale = CLAMP (zoom, ZOOM_OUT_MAX, ZOOM_IN_MAX);
+        m_Scale = CLAMP (zoom, ZOOM_FACTORS[0], ZOOM_FACTORS[MAX_ZOOM_STEPS-1]);
+        for (idx = 1; idx < lim; ++idx)
+            if ( CLAMP ( m_Scale, ZOOM_FACTORS[idx-1], ZOOM_FACTORS[idx] )
+                 == m_Scale )
+                m_zoomStepsPerformed = idx - 1;
         refreshCache ();
         G_UNLOCK (JobRender);
         notifyPageZoomed ();
@@ -1270,10 +1280,7 @@
 void
 IDocument::zoomIn (void)
 {
-    if (canZoomIn ())
-    {
-        setZoom (getZoom () * ZOOM_IN_FACTOR);
-    }
+    zoomInOutWrapper(0);
 }
 
 ///
@@ -1287,10 +1294,41 @@
 void
 IDocument::zoomOut (void)
 {
-    if (canZoomOut ())
+    zoomInOutWrapper(-1);
+}
+
+///
+/// @brief Zooms In or Out
+///
+/// Common routine for zoomIn() and zoomOut() to exclude code duplication when
+/// making decision on value which should be added or to substracted to the
+/// current zoom level
+///
+/// @param zoomDirection Points whether to zoom in or zoom out the document.
+///
+/// @see zoomIn() zoomOut()
+///
+void
+IDocument::zoomInOutWrapper (gint zoomDirection)
+{
+  if ( (zoomDirection < 0) ? canZoomOut () : canZoomIn () )
+  {
+    gdouble currentScale = getZoom ();
+
+    if ( ZOOM_FACTORS[m_zoomStepsPerformed] == currentScale )
+      m_zoomStepsPerformed += (zoomDirection == 0) ? 1 : -1;
+    else
     {
-        setZoom (getZoom () * ZOOM_OUT_FACTOR);
+      gint idx;
+      gint lim = MAX_ZOOM_STEPS - 1;
+
+      for ( idx = 1; idx < lim; ++idx )
+        if ( CLAMP ( currentScale, ZOOM_FACTORS[idx-1], ZOOM_FACTORS[idx] )
+             == currentScale )
+          m_zoomStepsPerformed = idx + zoomDirection;
     }
+    setZoom ( ZOOM_FACTORS[m_zoomStepsPerformed] );
+  }
 }
 
 ///
diff -ruN a/src/IDocument.h b/src/IDocument.h
--- a/src/IDocument.h	2009-09-06 17:32:59.540845309 +0800
+++ b/src/IDocument.h	2009-09-06 17:37:03.134071681 +0800
@@ -357,7 +357,7 @@
 
         protected:
             static GQuark errorQuark;
-            
+
             IDocument (void);
             void addPageToCache (gint pageNum);
             PageCache *getCachedPage (gint pageNum);
@@ -412,6 +412,11 @@
             gchar *m_Subject;
             /// The document's title.
             gchar *m_Title;
+
+    private:
+            void zoomInOutWrapper (gint zoomDirection);
+
+            gint m_zoomStepsPerformed;
     };
 }