Is it permissible to download and print books unavailable in libraries for personal use, and to take video clips from YouTube and modify them by adding audio effects such as the Qur’an, knowing that these clips may be owned by non-Muslims?

If the use of the book is permitted without purchasing it, then there is no harm in downloading and printing it for personal use. However, if it is not permitted, then it is not permissible to download or print it, even for non-commercial personal use; because copyrights and publishing rights are owned by their proprietors, and it is not permissible to infringe upon them.