Yes, there are plenty of calculus PDFs available online that can help your friend learn and understand the subject better. Some good resources include textbooks, lecture notes, and practice problems with solutions. Your friend can also look for online courses or video tutorials that provide PDF notes for further review and understanding. It's important for your friend to actively engage with the material and practice solving problems to truly grasp the concepts. Additionally, participating in online forums or study groups can also be helpful for discussing and clarifying any questions your friend may have. Encourage your friend to take advantage of these resources and put in the effort to truly understand calculus.