Embedding an image without using www folder in Shiny

I have an application where I want to display files that people upload to my shiny-server.

I know how to accomplish this usings tags$iframe and the www folder. Is there any way I can embed an image or pdf without using the www folder? I want the file to be secure. Thanks!

What do you mean with secure?
Who should upload the file and who should see the file?
Just the same user, noone else?

So if I leave a file in the www folder, it's easily accessible with a URL:

mywebsite.com/path_to_file.pdf. Normally my shiny app run on mywebsite.com has a log-in and password. So data.table and other things that are displayed in the app are protected through my HTTPS. I was wondering if there was something similar for embedded pictures/pdfs

I don't want someone to be able to access the files through that URL bypassing the log-in/password process