Unless you are going to fully digitise every document and then have a searchable index then you may already have them accessible. The project will take some time and depends on the condition of the documents and who they are fastened together. ADF's do not like staples or paperclips. Most, if not all, scanners come with OCR software that will convert the scanned image into a word document. The degree of accuracy varies and depends on the program, the quality of the original and that layout that is scanned.
Hope someone else can give you a better pointer to hardware, etc.