If the OCR output is from Searchable Image or Searchable Image Exact then Acrobat Pro can remove it.
For Acrobat X:
Tools > Protection > Remove Hidden Information
In the Remove Hidden Information pane click the "Remove" button.
If the tick is present adjacent to the Hidden Text entry then the OCR output is removed.
For Acrobat 9:
Document > Examine Document
In the Examine Document pane click the "Remove" button.
If the tick is present adjacent to the Hidden Text entry then the OCR output is removed.
For Acrobat 8:
Document > Examine Document
In the Examine Document dialog click the "Remove all checked items" button.
If the tick is present adjacent to the Hidden Text entry then the OCR output is removed.
Be well...