Adobe ExportPDF supports optical character recognition, or OCR, when you convert a PDF file to Word (.doc and .docx), Excel (.xlsx), or RTF (rich text format). OCR is the conversion of images of text (scanned text) into editable characters, so that you can search, correct, and copy the text.
When OCR is enabled, Adobe ExportPDF performs OCR on PDF files that contain images, vector art, hidden text, or a combination of these elements. (For example, Adobe ExportPDF performs OCR on PDF files created from scanned documents.) Adobe ExportPDF also performs OCR on text that it can't interpret because the text was encoded incorrectly in the source application.
If you don't want Adobe ExportPDF to convert images of text to editable text, consider disabling OCR. When OCR is disabled, Adobe ExportPDF can process the document more quickly. Likewise, if the PDF you're converting contains a mix of formatted text and graphics, and you want to leave the graphics as is, disable OCR. Finally, you can disable OCR if you find that Adobe ExportPDF doesn't interpret text correctly (because it was encoded incorrectly).