Some version of this has been floating around the Internet since 2007, probably earlier. This tweet is pretty emblematic of posts about this claim: it’s stated as pure fact, with no supporting evidence or explanation. We’re meant to just accept that a single PDF can only cover about half the area of Germany, and we’re not given any reason why 381 kilometres is the magic limit.

I started wondering: has anybody made a PDF this big? How hard would it be? Can you make a PDF that’s even bigger?

A few years ago I did some silly noodling into PostScript, the precursor to PDF, and it was a lot of fun. I’ve never actually dived into the internals of PDF, and this seems like a good opportunity.

Let’s dig in.