I would like to know how I can block specific urls

I would like to know how I can block specific urls to different memebership tiers or access levels?

I have specific links to PDF files (I am using Flexpaper to show them) in a folder.
File structure: public_html/pdfs/file name
Link: domain.com/pdfs/filename

My website is in a subfolder: public_html/domain/wp-content....
Website URL: domain.com

How can I use Protected Content or the Membership plugin to block the URLs to where my files/links are located?

I can move the pdf file structure into my WP-Content folder etc.. but would than like to hid/mask the URL so it doesn't show the entire link structure.

Any help is appreciated.