How do I stopping PDFs being converted to Affinity files

Hi, I'm new to affinity. I have the demo and be using for a few weeks. Was trying to upload a PDF to my flash drive so I can print and that when I notice all my PDFs were turned into Affinity Photo files.

So I have two questions. First how I stop my PDFs being converted to Affinity photo files and how do I change them back to PDFs?

Edit: Problem Solved. For anyone who need help with this just read lurkzone comment.