Not a direct answer, but when making your choice, you may consider to choose something that does Optical Character Recognition (OCR) on the fly. This gets you searchable PDFs that also allow for selecting the text.
So: software that puts a "layer" of selectable and searchable text behind the scanned image.
In fact many Canon scanners come with OmniPage SE as both a standalone application and also tightly integrated in the scan tasks. When using the Canon software to scan directly to PDF, Omnipage SE works in the background without any human intervention. So: it is not 100% accurate, but the Canon solution works quickly and user friendly.
(The creator of OmniPage also sells the cheaper PDF Converter Professional, which as of version 6 can scan directly to PDF and can do more magic on PDF for you. Some fancy PDF readers may do the OCR on the fly as well, even if not included in the document. That will not allow searching from the operating system though, unless the operating system includes OCR by itself.)