You can remove unused IPTC keywords from the ACDSee Pro database. Once removed, the IPTC keywords will no longer display under Keywords (IPTC) in the Photo Properties' Auto Categories list of the Catalog Pane.
This process also applies for the Supplemental Categories field. This field is only visible if selected from the Choose Metadata to Display dialog box found under Tools | Options | Properties Pane by pressing the Manage Metadata Views button.
To remove IPTC keywords and supplemental categories:
To select more than one keyword, press and hold the CTRL key while selecting the keywords.
Only keywords that are not in use can be removed from the list. To find photos associated with a keyword, click the keyword listed under Photo Properties in the Auto Categories list of the Catalog pane.