I'm developing a book-store WordPress website where you can purchase and download books in PDF format. I don't want to use the local space for file storage (the host provider offers cheaper solutions for "download servers").
What I want to achieve
Every time my client tries to upload a new book to the website through media library upload feature, WordPress can detect that it's a PDF file and automatically upload it to the Download Server and save that URL (e.g. books.mywebsite.com/books/novel/the-new-book.pdf ) into the database along with it's attachment data.