A poster is the cheapest way to cover a large area, and for a message that lasts a few weeks, that’s often just enough. The question isn’t whether the paper is strong enough, but where it’s displayed.
For outdoor use, there is blueback, paper with a blue reverse side. This blue prevents whatever is underneath from showing through the new poster, which is important when you’re sticking it over a previous campaign. It is applied using wallpaper paste, either onto an existing panel or in a frame.
If there’s a light behind it, then it’s a lightbox poster on backlit paper. This is translucent and diffuses the LED light, so you can’t see the lights shining through it. That’s exactly what a normal poster in a lightbox does.
If the image is to remain on display for a season or longer, or if it needs to be removed without leaving any residue, then paper is not the right choice and you’ll need to opt for a textile canvas or a plate out.