[chaps]

They also support iframes! The absolute madness of PDFs is a world wonder. But I'm really still not sure we could do without them.

[bityard]

Gzipped PostScript documents were fairly popular during the 90's and are functionally identical to PDFs for 99% of use cases. (PDF is essentially PostScript, but with more features.)

[kccqzy]

For Gzipped PostScript, code execution is its raison d'être. But it is at least possible to build a PDF viewer without code execution.

[necovek]

Well, both a simpler language more geared toward presentation, but also including more modern features designed for on-screen viewing.