DPI scanner settings for OCR

Can someone tell me what are optimum DPI settings for OCR? I’m getting addicted to this function but the data base is getting humongous. Currently it is doing it in colour at 300DPI?

Also, whenever I export a pdf to acrobat for editing it says ‘File damaged’ and repairs it. I don’t notice any difference: is it damage or an incompatibility?

Many thanks for the sheets tip. (Duh!!)

The default settings are the optimum settings for most cases.