One problem is that Postscript is Turing complete, so it can be unreliable to parse. Not a great outcome if you just want to view a document. However, in reali

One problem is that Postscript is Turing complete, so it can be unreliable to parse. Not a great outcome if you just want to view a document. However, in reality I've often found it easier to write throwaway perl scripts to analyse/modify PS files rather than PDF. Writing a tool to target a set of PS files made by the same process usually isn't too hard unless there is something really unique going on - but it can be a problem generalising it to any random PS file. PDF is more structured so it can be easier to make general purpose tools, but in my line of work we prefer version 1.4 since the later versions add bloat that isn't necessary for print. It's also usually easier to consider them append-only, it's trivial to add content but editing is a lot harder due to offsets and references.