Extract words +1 and parser

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This is mostly a fan letter: thank you for keeping this library going. It is simply amazing.
The experimental "extract words” capability was a great help in a recent project. We had to deal with some docs that had a..lively… variety of fonts, so being able to break words on font characteristics was really useful.
This made me wonder: has anyone done a project that integrated pdfplumber with parser tools? We deal with many PDF formats, but they all have a family resemblance. It would be nice if I could build up a library of rules describing documents I have met. I am not sure a PEG. grammar or the like would work for rules, but has someone tried?