You can decompress the streams with mutool and edit the Postscript-like code in any editor, if you want. (That doesn't help a lot with editing text, of course...)
You’re better off converting to markdown with docling or markupsafe. But, if you’re careful, Qpdf offers an intermediate document format, like pandoc, but pandoc doesn’t read PDF.
Monkt.com offers an online version (no setup or configuration) for docling. Additionally, it has a few extra extraction methods. It could be tested for conversion to markdown.