Parallel Processing for function **extract_pages**

[TheCutestCat]

Thanks for your great work!

I'm looking to improve processing speed by parallelizing the pdfminer.high_level.extract_pages function, which currently uses a generator and doesn't support parallel execution. I've attempted parallel processing but encountered resource conflicts.

Are there any plans to implement parallel processing for this function? I understand this might require significant underlying changes. I'd be happy to contribute to this effort.