PDF files are OCR'd and searchable in Preview, but Spotlight is unable to find
I use Microsoft OneDrive to sync all of my scanned invoices, bills, and receipts for my business to my home and work computers. At the office I have a newer HP desktop with Windows 8.1 with OneDrive built in natively. At home I use a 4+ year old iMac running Mavericks and the OneDrive app from the Appstore. Everything syncs just fine.
The problem is that when I want to search for invoices coded to one of our job codes, "5801" for example, Spotlight is unable to locate anything. However, when I open a scanned pdf containing "5801", it is able to easily find it and highlight it within Preview.
My Windows 8.1 desktop has the ability to search "5801" and find every pdf containing "5801", so I know it's possible.
I have installed the latest OneDrive updates, removed the OneDrive folder from Spotlight indexing twice (to then reindex), and nothing has worked.
Any ideas?
iMac, Mac OS X (10.6.8)