Improve PDF parsing

[cbldev]

Actual behavior

I noticed that on some complex PDF, with tables, pdftotext produce better result than pdf-reader gem.

pdftotext: https://www.xpdfreader.com/pdftotext-man.html

Issue in Langchainrb: https://github.com/patterns-ai-core/langchainrb/issues/682

Expected behavior

Good results on complex PDF parsing.