exempt pdf view from xframe_options:deny

lms/djangoapps/staticbook/views.py

@@ -3,6 +3,7 @@ Views for serving static textbooks.
 """
 
 from django.contrib.auth.decorators import login_required
+from django.views.decorators.clickjacking import xframe_options_exempt
 from django.http import Http404
 from opaque_keys.edx.keys import CourseKey
 
@@ -60,6 +61,7 @@ def remap_static_url(original_url, course):
 
 
 @login_required
+@xframe_options_exempt
 def pdf_index(request, course_id, book_index, chapter=None, page=None):
     """
     Display a PDF textbook.