For what it's worth, I, as an otherwise not too active person in this thread, like Krewinkel's "folded paper" suggestion.
I believe it scales better than other suggestions, is simpler and still gives immediate associations to paper and thus documents.

On a second for me is Insanes split-paper logo. I think the rotated-symmetry ones are too involved and convoluted.



Den måndag 12 december 2016 kl. 16:45:22 UTC+1 skrev Albert Krewinkel:

I am a huge fan of very simple logos, so here is another suggestion (very rough sketch): It's a piece of paper (letter or a4) folded in two places.  The result resembles both a "p" and "d" as well as an mathematical integral sign (as pandoc "integrates" all document formats into a single type). This would probably look best using two, or maybe three, colors.