diff --git a/Pdf4QtLib/sources/pdfdocument.h b/Pdf4QtLib/sources/pdfdocument.h
index 6a0d5f8..d6b11ac 100644
--- a/Pdf4QtLib/sources/pdfdocument.h
+++ b/Pdf4QtLib/sources/pdfdocument.h
@@ -553,6 +553,7 @@ public:
 
     bool hasReset() const { return m_flags.testFlag(Reset); }
     bool hasPageContentsChanged() const { return m_flags.testFlag(PageContents); }
+    bool hasPreserveUndoRedo() const { return m_flags.testFlag(PreserveUndoRedo); }
     bool hasFlag(ModificationFlag flag) const { return m_flags.testFlag(flag); }
 
     operator PDFDocument*() const { return m_document; }
diff --git a/Pdf4QtViewer/pdfviewermainwindow.cpp b/Pdf4QtViewer/pdfviewermainwindow.cpp
index 89c639b..d94f016 100644
--- a/Pdf4QtViewer/pdfviewermainwindow.cpp
+++ b/Pdf4QtViewer/pdfviewermainwindow.cpp
@@ -464,7 +464,7 @@ void PDFViewerMainWindow::setDocument(const pdf::PDFModifiedDocument& document)
         {
             m_sidebarDockWidget->hide();
         }
-        else
+        else if (document.hasReset() && !document.hasPreserveUndoRedo())
         {
             m_sidebarDockWidget->show();
         }