Big Sky S03e05 | Stagatv.com.mkv.mkv -

The file extension .mkv.mkv suggests the file may have been renamed incorrectly or is from a third-party distribution site. Ensure you have a reliable antivirus active when downloading associated "papers" or subtitle files from unofficial sources.

: These are text files containing technical info about the video rip (bitrate, encoder, source). These are usually bundled in the original download folder from sites like STAGATV. Big Sky S03E05 | STAGATV.COM.mkv.mkv

Since "paper" is not a standard technical term for video files, you are likely looking for one of the following: The file extension