diff --git a/app/api/projects_api.rb b/app/api/projects_api.rb
index fb88a683a..c2954bdcb 100644
--- a/app/api/projects_api.rb
+++ b/app/api/projects_api.rb
@@ -215,4 +215,17 @@ class ProjectsApi < Grape::API
     present portfolio_tasks.map(&:id)
   end
 
+  desc 'Get IDs of tasks that are still processing a PDF '
+  get '/projects/:id/tasks_processing' do
+    project = Project.find(params[:id])
+
+    unless authorise? current_user, project, :get
+      error!({ error: "Couldn't find Project with id=#{params[:id]}" }, 403)
+    end
+
+    portfolio_tasks = project.tasks_processing_pdf
+
+    present portfolio_tasks.map(&:id)
+  end
+
 end
diff --git a/app/models/pdf_generation/project_compile_portfolio_module.rb b/app/models/pdf_generation/project_compile_portfolio_module.rb
index 3ad5d1eb5..eab5a5292 100644
--- a/app/models/pdf_generation/project_compile_portfolio_module.rb
+++ b/app/models/pdf_generation/project_compile_portfolio_module.rb
@@ -205,6 +205,19 @@ def portfolio_tasks
       end
     end
 
+    # Return the tasks that are currently being processed
+    def tasks_processing_pdf
+      # Get assigned tasks that should be included in the portfolio
+      tasks = self.tasks.joins(:task_definition).order('task_definitions.target_date, task_definitions.abbreviation')
+
+      # Select tasks that should have a PDF submission, but is currently being processed
+      tasks.select do |task|
+        !task.has_pdf &&
+          task.processing_pdf? &&
+          task.task_definition.upload_requirements.present?
+      end
+    end
+
     #
     # Return the path to the student's learning summary report.
     # This returns nil if there is no learning summary report.
diff --git a/test/models/project_model_test.rb b/test/models/project_model_test.rb
index b237689de..ea53a4a33 100644
--- a/test/models/project_model_test.rb
+++ b/test/models/project_model_test.rb
@@ -131,6 +131,49 @@ def test_create_empty_portfolio
     unit.destroy!
   end
 
+  def test_portfolio_tasks_excludes_tasks_until_pdf_processing_finishes
+    unit = FactoryBot.create(:unit, with_students: false, task_count: 0)
+    project = FactoryBot.create(:project, unit: unit)
+    no_upload_task_definition = FactoryBot.create(:task_definition, unit: unit, upload_requirements: [])
+    finished_task_definition = FactoryBot.create(:task_definition, unit: unit)
+    processing_task_definition = FactoryBot.create(:task_definition, unit: unit)
+
+    no_upload_task = FactoryBot.create(
+      :task,
+      project: project,
+      task_definition: no_upload_task_definition,
+      task_status: TaskStatus.ready_for_feedback
+    )
+    finished_task = FactoryBot.create(
+      :task,
+      project: project,
+      task_definition: finished_task_definition,
+      task_status: TaskStatus.ready_for_feedback
+    )
+    processing_task = FactoryBot.create(
+      :task,
+      project: project,
+      task_definition: processing_task_definition,
+      task_status: TaskStatus.ready_for_feedback
+    )
+
+    FileUtils.touch(finished_task.final_pdf_path)
+    FileUtils.touch(processing_task.final_pdf_path)
+    processing_dir = FileHelper.student_work_dir(:new, processing_task, true)
+
+    assert_includes project.portfolio_tasks, no_upload_task
+    assert_includes project.portfolio_tasks, finished_task
+    assert_not_includes project.portfolio_tasks, processing_task
+    assert_includes project.tasks_processing_pdf, processing_task
+
+    FileUtils.rm_r(processing_dir)
+
+    assert_includes project.portfolio_tasks, processing_task
+    assert_not_includes project.tasks_processing_pdf, processing_task
+
+    unit.destroy!
+  end
+
   def test_create_portfolio_with_lsr
     project = FactoryBot.create(:project)
     unit = project.unit