Yep. I've been using a similiar service (chatpdf.com) and uploading amateur radio mathematics pdfs and portions of the arrl handbook. I can't quite upload the entire thing due to size constraints, but I've been able to do quite a bit of Q&A from the book chapters.

This Ask your Pdf allows up to 20MB for free vs chatpdf's 10MB free; though chatpdf has a 32MB allowance on the paid plain. Not sure how how ask your pdf plans to monetize this.

I'm personally looking into setting up my own self-hosted "chatpdf/askyourpdf" clone so I can put put a whole bunch of my reference material in there. I can't actually open it up as a service because of the copyrighted works, but I would really love to have ham Q&A site based on the ARRL Handbook and other resources. Even expand that out to an electronics Q&A.

There's a site called llamahub.ai that lets you load lots of your own resources into a LLM index so you can train GPT (or potentially the opensourceish gpt4all variant) on your own resources.