Originally posted by: TastesLikeChicken
Scanning software is built-in to XP and Vista. If you're using Linux there's a ton of freeware available.
Whatever comes with the OS ususally is very basic.
I recommend something like Nuance (formerly ScanSoft) PaperPort. This is fantastic software, and can do some conversion to PDF, as well as manage documents, and has OCR and imaging capabilities. You can by a previous version and save a little money.
There's actually two problems that you have -- What to use for scan, and how to convert it to PDF. Scan software will usually come with your scanner, including drivers. Any software that support scanning should be able to use your scanner drivers directly, so you should not need much additional software, if at all.
As for converting to PDF, you should look at getting something like a PDF printer. There are many companies (including Adobe) that have this. This would then allow any application that can print, to output a PDF. So, then you can use whatever application you want to scan, and then use it's printer functions to generate a PDF file.