How can i make the scan of PDF files more accurate? If there is a way.

I'd probably have to see what areas you are disappointed with the scans. Depending upon the type of error, I believe you can add a dictionary that can help with the OCR results. But truth be told, I have not done this yet myself to confirm because I like going through the editor that flags potential errors for me so I can review them one-by-one. I find the solution does a reasonable job with basic OCR recognition, and also does a good job of flagging potential errors that can be addressed as part of the conversion process. Again, not understanding exactly what type of issues you are encountering, it's hard to comment futher although ABBYY support should definitely be able to help.