A businessr-grade applications from Adobe and Nuance can do reasonably accurate OCR (Optical Character Recognition) on page scans and save the files with a searchable layer.
Certain production-grade xerox MFP's that have Fiery print controllers with an optional OCR feature installed can perform OCR on scanned pages on the fly and save the file as a searchable PDF.
What this means is, that a printed document can be converted to a PDF file that is searchable by keyword. The OCR process is most reliable when processing common fonts such as Arial, Times New Roman, etc. It doesn't work reliably or at all with script fonts or handwritten longhand. Poor-quality documents of limited contrast, are dirty or otherwise cosmetically challenged will result in errors in the OCR process that may result in characters being mis-identified.
It's resource-intensive and not very fast, and the Fiery searchable PDF output feature is expensive. Some larger print shops will have equipment with this capability, especially those in close proximity to city halls, a concentration of law firms and courthouse complexes.
Fiery is a brand of high-end print controllers (RIPs - Raste Image Processors) common to high-volume B&W and color on-demand printing.
When I was doing the Network Analyst gig with xerox, I'd use our showroom units to make searchable PDFs for myself. Sometimes I'd use a customer's unit if I had to have it down for scan testing anyway.
Don't know what a print shop would charge to scan & convert; guessing $.05 per page for a bound manual, less for loose pages. A bound manual would slow the scan process because every page would have to be scanned individually on the glass instead of being fed through a document feeder, so it's time consuming for the operator.
Good Ridin'
slmjim
