Many recent scanners come with a pdf scanning software installed, even the very reasonaby priced Cannon scaner I recently brought, to replace my dieing old one. One thing to note is not to scan in to too smaller size files as it may look good on screen, but in print, unreadale.
Another economical way to a pdf scan on the cheap, is many newish office copiers come with a scannig to e-mail function, and as a bonus most come with an automatic feed system and double side scanning.