Open this from the Additional characters or Reject character edit box in the OCR Options panel (Tools menu).
Greyed characters on the Character Map indicate that they are not enabled for recognition, although they can be inserted into the edit box. Right-click on an empty area below the character map and use the shortcut menu to display or hide character sets.
Select the desired additional characters or a single reject character and click OK.
The Character Map can display characters from a range of alphabets, providing your system and its font files support them. Choose View/Character Map/Character Sets and select more sets if you do not see the characters you need. Japanese, Chinese and Korean characters are not available.
The Character map is also displayed in the OCR Proofreader and in the Text Editor for entering non-keyboard characters.