Is it necessary to obtain permission from the Ministry of Islamic Affairs, Endowments, Da‘wah, and Guidance in the Kingdom of Saudi Arabia before uploading a PDF volume of the collection of Fatwas by Sheikh Al-Islam Ibn Taymiyyah, may Allah have mercy on him?

You are not required to seek permission from the Ministry to download the fatwas unless there is a text prohibiting it, because the printing entity is not a commercial establishment, and the book is printed under the supervision of the Ministry of Islamic Affairs. There is no harm in downloading it unless the entity explicitly prohibits copying or downloading without its permission. In that case, adherence to this prohibition is obligatory, even if the download is for personal use.