How to prevent downloading of pdf files in our root folder

I have made a firebase website where I can put my pdf files in public directory when someone opens my website will show "you can't access this website its a private website." but when they visit it also downloads the pdf files in the root directory which is actually not displaying in the website which increases my bandwidth unnecessarily but I want to access it like www.domain.com/myfile.pdf which is not a problem for me but the problem is how to prevent the usage of bandwidth where just viewing my website it increases It should be accessible like www.domain.com/myfile.pdf that's all, but it should not get downloaded from www.domain.com please help me