Are there images in this scanned PDF? There is a possibility of images or something else throwing off the Abby Reader. Using the parameter "OCR Dictionary Type" you can specify what type of characters for OCR to look for and output. This parameter may help in removing the junk values that you see. http://help.openspan.com/80/Components/DocumentOCR_Component.htm
The OCR component is not guaranteed to work with handwritten text. Unfortunately, it was not designed to work with handwritten text. The component was originally designed for printed documents that are scanned (rather than written text). Further explanation can be found on ABBYY's KB Articles - https://abbyy.technology/en:kb:faq:recognizing_handprinted_text.