How do I stop unknown downloads on my samsung s5?

Okay, I currently have a site called cub_seismic...I in this spot are, numbers between 1--14 and then it finishes off with .pdf. So, obviously, I've been having this site or, whatever, downloading something at least 1 to 2 times per day. Now, I have absolutely no idea what this is. Is there antyway you can help me stop this, I dont know if its hurting my phone or using up a lot of memory or what, I heard you guys were really good at what you do. Please, help me.

Welcome to Android Central! What do you mean that you "currently have a site"? Are you saying that the phone is notifying you of these downloads, and you're guessing they're from a website called "cub_seismic"?

What's the full filename for these pdf files?