I recently completed running an international conference. I hope to make certificates in a landscape orientation for the organizing committee, and some other attendees. In order to make everything easier, I'm trying to use LaTeX to script as much as possible. I've made a lot of headway outside the fact that there are different page sizes, paper, A4, etc.
I'm trying to make a background that looks likes this (ignore the non-framing, I lifted it from a JPG that was in a Word document used in past conferences):
Specifically, I the blue double-line on the outside. I cannot seem to figure out how to make it programmatically so that I can use letter or A4 paper, and just math my way to success.
If anyone knows programmatically how to create this look, any guidance would be appreciated.

