Criteria

I'm assuming that you wish to end up with a PDF.

Acrobat can do that. 

I have Office 365 (for the Mac); I'm not fully sure what aspect you want out of a PDF that will work the O' 365. Can you elaborate on that?

As far as searchable, it will be by the text. However, I have to put out one big caveat to that: ALL OCR software can make mistakes by itself, and in addition to that, if documents are poorly scanned, or the originals are poor quality, the results will go downhill from there.

Too many people think that scanning is scanning and it doesn't make a difference, but it certainly does. If you do not adjust the scan so that the white page is fully white and the text on the other side of the page has been removed, and you're scanning at a high resolution, the quality of the OCR will go down significantly. Text with "ri" will be seen as an "n," and things like that. 

To add to this, I know of no OCR package that will combine hyphenated words successfully (and Acrobat doesn't do that at all).

To sum this issue all up, if you search for a specific word (or phrase) and the word was not OCRed correctly, it will not be found. So, the better quality of the scan, the better chance you'll have with the OCR results.

I wrote this some time back for Adobe; it may give you a better idea of what is required for good-quality scans.

Scanning Clean, Searchable PDFs 

https://community.adobe.com/t5/acrobat-discussions/scanning-clean-searchable-pdfs/td-p/4785435