diff --git a/app/models/document.rb b/app/models/document.rb
index b42c78f..6410dda 100644
--- a/app/models/document.rb
+++ b/app/models/document.rb
@@ -10,9 +10,9 @@ class Document < ApplicationRecord
 
   #### VALIDATIONS
   validates_presence_of :file, :user, :thesis
-  validate :primary_file_presence, on: :create
-  validate :supplemental_file_must_be_file_types
-  validate :primary_file_must_be_pdf
+  validate :one_primary_file_per_thesis, on: :create
+  validate :validate_extension
+  validate :validate_usage
 
   #### SCOPES
   scope :newest, -> { order('created_at desc') }
@@ -28,7 +28,8 @@ class Document < ApplicationRecord
   enum usage: %i[thesis embargo embargo_letter licence]
 
   attribute :usage, default: :thesis
-
+  attribute :supplemental, default: true
+  attribute :deleted, default: false
 
   PRIMARY_FILE_EXT = [ '.pdf' ].freeze
   SUPPLEMENTAL_FILE_EXT = ['.pdf', '.doc', '.docx', '.txt', '.html', '.htm', '.odt', '.odp',
@@ -41,14 +42,14 @@ def allowed_extensions
     list = PRIMARY_FILE_EXT
 
     case document_type
-    when 'primary'
-      list = PRIMARY_FILE_EXT
     when 'supplemental'
       list = SUPPLEMENTAL_FILE_EXT
     when 'licence'
       list = LICENCE_FILE_EXT
     when 'embargo'
       list = EMBARGO_FILE_EXT
+    else
+      list = PRIMARY_FILE_EXT
     end
 
     return list
@@ -67,43 +68,48 @@ def display_name
     name
   end
 
+  def primary?
+    return !supplemental?
+  end
+
   ### CUSTOM VALIDATIONS
-  def primary_file_presence
-    if thesis && (thesis.documents.primary.not_deleted.size.positive? && supplemental? == false && deleted? == false)
-      errors.add(:file, 'You can only upload one primary file per thesis')
+  def one_primary_file_per_thesis
+    if primary? && !deleted? && thesis && thesis.has_primary_file?
+      errors.add(:file, 'Only one primary file allowed.')
     end
   end
 
-  def primary_file_must_be_pdf
-    return unless file.filename.present? && !supplemental
-
-    return if file.filename.downcase.end_with?('.pdf')
-
-    errors.add(:file, "extension #{ext} is not allowed.")
+  def file_extension
+    return nil unless file.filename.present?
+    ext = '.' + file.filename.downcase.split('.').pop
   end
 
-  def supplemental_file_must_be_file_types
-    supplemental_file_types = SUPPLEMENTAL_FILE_EXT
-    embargo_file_types = EMBARGO_FILE_EXT
-
-    return unless file.filename.present? && supplemental
+  def validate_extension
+    if !valid_extension?
+      errors.add(:file, "Extension #{file_extension} is not allowed.")
+    end
+  end
 
-    ext = '.' + file.filename.downcase.split('.').pop
+  def valid_extension?
+    return allowed_extensions.include? file_extension
+  end
 
-    if document_type == "licence"
-      return if file.filename.downcase.end_with?('.pdf')
-    elsif document_type == "supplemental"
-      return if supplemental_file_types.include?(File.extname(file.filename.downcase))
-    elsif document_type == "embargo"
-      return if embargo_file_types.include?(File.extname(file.filename.downcase))
+  def validate_usage
+    if !valid_usage?
+      errors.add(:usage, 'Primary file usage must be "thesis".')
     end
+  end
 
-    errors.add(:file, "extension #{ext} is not allowed.")
+  def valid_usage?
+    if primary? && usage != 'thesis'
+      return false
+    end
+    return true
   end
 
   def document_type
     return 'supplemental' if self.usage == "thesis" && self.supplemental?
-    return 'primary' if self.usage == "thesis" && !self.supplemental?
+    return 'primary' if self.usage == "thesis" && self.primary?
     return 'embargo' if self.usage == "embargo" || self.usage == "embargo_letter"
     return 'licence' if self.usage == "licence"
   end
diff --git a/app/models/thesis.rb b/app/models/thesis.rb
index 97d0e10..41d83c3 100644
--- a/app/models/thesis.rb
+++ b/app/models/thesis.rb
@@ -197,4 +197,8 @@ def publish
   def self.assigned_to_user(user)
     Thesis.where('assigned_to_id = ?', user.id)
   end
+
+  def has_primary_file?
+    return documents.primary.not_deleted.size > 0
+  end
 end
diff --git a/test/models/document_test.rb b/test/models/document_test.rb
index cbcb6c5..5d1cdf2 100644
--- a/test/models/document_test.rb
+++ b/test/models/document_test.rb
@@ -25,6 +25,31 @@ class DocumentTest < ActiveSupport::TestCase
     assert !build(:document, file: nil).valid?, 'File is required'
     assert !build(:document, user: nil).valid?, 'User/owner is required'
     assert !build(:document, thesis: nil).valid?, 'Thesis is required'
+
+    # should not be able to create a primary file with extension .jpg 
+    doc = build(:document, usage: 'thesis', supplemental: false, file: fixture_file_upload('image-example.jpg'))
+    assert '.jpg', doc.file_extension
+    assert !doc.valid_extension?, 'extension .jpg should not be valid for primary file'
+    assert doc.primary?, "must be primary"
+    assert !doc.supplemental?, "must not be supplemental"
+    assert_equal 'thesis', doc.usage, 'usage must be "thesis"'
+    assert !doc.valid?, 'Should not be valid, extension cannot be .jpg'
+
+    # should not be able to create a primary file with usage "licence"
+    doc = build(:document, usage: 'licence', supplemental: false, file: fixture_file_upload('pdf-document.pdf'))
+    assert '.pdf', doc.file_extension
+    assert doc.valid_extension?, 'extension should be valid'
+    assert doc.primary?, "must be primary"
+    assert_equal 'licence', doc.usage, 'usage must be "licence"'
+    assert !doc.valid?, 'Should not be valid, usage can not be "licence" AND not supplemental'
+
+    # should not be able to create a primary file with usage "embargo"
+    doc = build(:document, usage: 'embargo', supplemental: false, file: fixture_file_upload('pdf-document.pdf'))
+    assert '.pdf', doc.file_extension
+    assert doc.valid_extension?, 'extension should be valid'
+    assert doc.primary?, "must be primary"
+    assert_equal 'embargo', doc.usage, 'usage must be "embargo"'
+    assert !doc.valid?, 'Should not be valid, usage can not be "embargo" AND not supplemental'
   end
 
   should 'only allow one primary file per thesis, and it should ignore deleted' do