[DSpider]

My advice is NOT to scan them directly as PDF, but as images (preferably TIFF or PNG). Then run the images through Scan Tailor and then through ABBYY FineReader if you want some search functionality. This is the "quick and dirty" way.

The "slow and of-an-exceptionally-high-quality way" would be to OCR it with ABBYY FineReader Professional, proofread the entire thing, process the graphics, track down the fonts, redo the layout in Word or InDesign, export as PDF (and maybe tweak a few things in Acrobat), and proofread again the final product. Not many people are willing to spend the time and effort for this, but the result is of very high quality. It's always a pleasure to read such a book. But first make sure that it's worth it, and that it's not already available as an e-book.

Open-source alternatives: LibreOffice, GIMP, Scribus.