Why you should clean up image PDFs
The quality of PDF images varies greatly, and it depends on a number of factors. When you scan a document into PDF, the resulting image file is not always crystal clear. Its resolution depends on the quality of the scanner that you are using, as well as the clarity of the original document. However, if the image contains scanned text and you want to OCR that text, you should clean up the image in order to get accurate OCR results.

Batch processing PDF software
Any type of software for working with scanned documents can be designed for different volumes of information. Programs that are slow might be adequate for single use, but they will not meet your requirements if you scan documents in bulk. For that, you would need software with batch processing capabilities, which can accelerate image processing by handling the documents in large groups, or batches.
How to batch clean image PDFs
Consider an instance where you have scanned many pages of text on an imperfect scanner, and your resulting files are somewhat skewed. If you want to OCR that text, an OCR tool with batch processing and de-skewing capabilities would be an excellent tool. Maestro Recognition Server is a batch OCR tool that has advanced image processing, such as de-skewing and de-speckling. You can try Maestro for free just by downloading the trial version from CVISION Technologies.