> Assuming it's based on Poppler 0.5 or later (into which xpdf 3.02 changes were merged,
> bringing pdf 1.6/1.7 support). But since that was released in 2007, I think it's a safe bet. ;o)

Yes, your assumption seems reasonable. After all, enclosing a new PDF viewer and basing it on (something that is based on) pre-3.02 Xpdf wouldn't make sense as this would lack advantage over current Apdf 3.4, which is based on Xpdf 3.01.