not being able to ctrl-F a textbook or have click-to-chapter links sure makes studying harder these days... and any scanning software worth it's salt will at least do the bare minimum OCR automatically...
There are a bunch of online tools that are free and let you upload a PDF to have it go through OCR.
Just Google "Free PDF OCR" and click through all the ads to upload, then give them a temporary email address to get a download link to the finished product.
Hot tip: There are free temporary email address sites too, if you need one to avoid getting on their ad lists.