Actually, PDF is a turing complete programming language.
PDF is a simplification and wrapper around the computer language PostScript - a PostScript or PDF doc literally runs on the printer or computer and outputs the rasterisation of the thing you want to print.
PostScript is language based around a stack. You can define functions (which may be fully recursive) that run on the stack.
Here’s a small example:
/ANGLE {
newpath
100 0 moveto
0 0 lineto
100 50 lineto
stroke
} def
10 setlinewidth
0 setlinejoin
100 200 translate
ANGLE
1 setlinejoin
0 70 translate
ANGLE
2 setlinejoin
0 70 translate
ANGLE
As such, PDF that’s actually similar to Python, and HTML is closer to something like a JSON or XML document.
Note however that HTML can contain Javscript or WASM programs, but these are embedded rather than features of HTML.
Interestingly C and D are both programming languages. That is, there is a programming languages called C and another, D.
I’ll see myself out…