Replace routes.py

blog/routes.py

 from flask import render_template, url_for, request, redirect, flash, Response, send_file, abort
 from blog import app, db
+import os
 from blog.models import User, Post, Portfolio
 from blog.forms import RegistrationForm, LoginForm, UpdateAccountForm, PostForm
 from flask_login import login_user, logout_user, current_user
@@ -24,8 +25,8 @@ def cv():
 
 @app.route('/download')
 def download():
-  path = "static/pdf/cv.pdf"
-  return send_file(path, as_attachment=True)
+  file_path = os.path.join(os.getcwd(), "blog", "static", "pdf", "cv.pdf")
+  return send_file(file_path, as_attachment=True)
 
 @app.route("/blog")
 def blog():