Quoting the Acrobat X SDK:
Changes to search object
The following changes have been made to the "search" object properties:
● The thesaurus and soundex properties have been removed
● The legacySearch property is now deprecated and always returns false.
Changes to SearchExecuteQuery
The following have been removed from nWordOptions parameter of SearchExecuteQuery:
The function SearchIsLegacySearchAvailable has been deprecated and will always return false.