diff --git a/Gemfile b/Gemfile
index 1eddd7b5..ef3a9e0d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -146,3 +146,5 @@ gem 'iiif_print', git: 'https://github.com/scientist-softserv/iiif_print.git', b
 gem 'order_already'
 gem 'redis', '~> 4.0'
 gem 'redlock', '~> 1.2.1'
+# locking to 5.1.0 because it was throwing errors on 5.3.0 in development
+gem 'simple_form', '5.1.0'
diff --git a/Gemfile.lock b/Gemfile.lock
index 756d4b4b..a09ae49f 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1035,7 +1035,7 @@ GEM
       faraday (>= 0.17.5, < 3.a)
       jwt (>= 1.5, < 3.0)
       multi_json (~> 1.10)
-    simple_form (5.3.0)
+    simple_form (5.1.0)
       actionpack (>= 5.2)
       activemodel (>= 5.2)
     simplecov (0.16.1)
@@ -1225,6 +1225,7 @@ DEPENDENCIES
   secure_headers
   selenium-webdriver
   sentry-raven
+  simple_form (= 5.1.0)
   simplecov
   solr_wrapper (~> 2.0)
   spring (~> 1.7)
diff --git a/app/helpers/pdf_js_helper.rb b/app/helpers/pdf_js_helper.rb
index 653ee81d..29e50f68 100644
--- a/app/helpers/pdf_js_helper.rb
+++ b/app/helpers/pdf_js_helper.rb
@@ -3,13 +3,13 @@
 module PdfJsHelper
   def pdf_js_url(file_set_presenter)
     # assumes that the download path exists if the file set has been characterized
-    path = if file_set_presenter.mime_type
-             hyrax.download_path(file_set_presenter.id)
-           else
-             file_set_presenter.solr_document["import_url_ssim"].first
-           end
+    url = if file_set_presenter.mime_type
+            "/pdf.js/web/viewer.html?file=#{hyrax.download_path(file_set_presenter.id)}"
+          else
+            file_set_presenter.solr_document["import_url_ssim"].first
+          end
 
-    "/pdf.js/web/viewer.html?file=#{path}##{query_param}"
+    url + "##{query_param}"
   end
 
   def pdf_file_set_presenter(presenter)
@@ -18,18 +18,23 @@ def pdf_file_set_presenter(presenter)
     # Commenting this line out because even PDFs that were not split will still have a representative media
     # which will be used first in this logic, consider uncommenting once all imports finish
     # representative_presenter(presenter) ||
-    first_file_set_pdf(presenter)
+    external_pdf(presenter)
   end
 
-  def first_file_set_pdf(presenter)
-    pdf_file_set_presenters = presenter.file_set_presenters.select(&:pdf?)
-    reader, archival = pdf_file_set_presenters.partition do |fsp|
+  def external_pdf(presenter)
+    reader, archival = pdf_file_set_presenters(presenter.file_set_presenters).partition do |fsp|
       fsp.solr_document["import_url_ssim"]&.first&.include? "READER"
     end
 
     reader.first || archival.first
   end
 
+  def pdf_file_set_presenters(presenters)
+    presenters.select(&:pdf?).presence || presenters.select do |file_set_presenter|
+      file_set_presenter.solr_document["label_ssi"].downcase.end_with? ".pdf"
+    end
+  end
+
   def representative_presenter(presenter)
     presenter.file_set_presenters.find { |file_set_presenter| file_set_presenter.id == presenter.representative_id }
   end
diff --git a/app/presenters/hyku/work_show_presenter.rb b/app/presenters/hyku/work_show_presenter.rb
index 5b631f9a..daaf34d6 100644
--- a/app/presenters/hyku/work_show_presenter.rb
+++ b/app/presenters/hyku/work_show_presenter.rb
@@ -31,13 +31,17 @@ def video_embed_viewer
 
     def pdf_viewer?
       return unless Flipflop.default_pdf_viewer?
-      return unless file_set_presenters.any?(&:pdf?)
+      return unless file_set_presenters.any?(&:pdf?) || pdf_extension?
 
       # If all of the member_presenters are file_set presenters, return true
       # this also means that there are no child works
       member_presenters.all? { |presenter| presenter.is_a? Hyrax::FileSetPresenter }
     end
 
+    def pdf_extension?
+      file_set_presenters.any? { |fsp| fsp.label.downcase.end_with?('.pdf') }
+    end
+
     def viewer?
       iiif_viewer? || video_embed_viewer? || pdf_viewer?
     end