You tell it what directories that you want to include/exclude from search, it indexes all the words and lets you search them. Its pretty fast and it includes and optional small semantic model for better intent search.

I built this mainly for the EE's at work that have a ton of component datasheets and they mentioned that it would be cool if this existed, they liked the prototype a lot and pushed me to share it. Recently i have also added some more useful features like comparing pdf's side by side (so you can view diagrams + pinout side by side) and a popup feature that allows you to "screenshot" a section of the pdf and have it always on top, along with some other cool things.

It's free and runs completely locally for obvious privacy reasons.