I think this is a pretty big ask, but I've got a whole lot of PDFs and would love to be able to search contents. As it is, you can't help with those that are just scans, but still a lot have text or could be converted.
I have nothing more intelligent to say about this. But if a question comes to mind, I'll try to answer.
Thanks for listening.
You can do this with PDF software such as Adobe Reader or PDF-XChange Editor using the advanced search or folder search feature. This allows you to perform a full-text search across all files in a folder.
I recommend Agent Ransack / FileLocator Pro for searching folders of PDFs.
IMHO it doesn't make sense for Matthias to put development effort into a feature that other specialised tools have invested years of effort into and therefore can perform that function much better.