About the post office opening mail for Atos

I am aware that the post offices are opening mail for Atos in supposedly secure areas of sorting offices and like many people I was really worried about my pdf form getting to them intact.

I tried to staple everything together but I sent lots of extra sheets and it wouldnt staple. It was last minute before post office closed so in a mad rush I punctured a hole with a screwdriver through all sheets and put one of those green paper connectors through but it was so loose there was about an inch gap and they were sliding around but I couldnt tighten it and my daughter had to leave with it or post office would close.
I'm now worried that sheets would rip and fall out. Does anyone know exactly how they stack them up? Is it as they come out of the envelope or do they connect them all together with a bolt ring or something so they at least keep them together