When something like this occurs, it’s usually an indication that the PDF file you are trying to convert has embedded fonts. To check if this is the case with your file, open the PDF in Adobe Reader, copy the problematic symbols and paste them into Notepad or MS Word. If they appear differently in these programs than they do in Adobe Reader, then you have a case of embedded fonts.
Before opening the PDF in Able2Extract Professional again, click on the View menu and select "Conversion Options…". In Conversion Options dialog, on the General tab, check the "Show unrecognized symbols as..." check-box. Once you convert the file again, simply use the Find and Replace command to enter the appropriate symbols.
This article refers to Able2Extract and Able2Extract Professional.