Enabling KM Search in the Document List 
Knowledge Management (KM) search uses the TREX system to index documents.
To enable KM search in the Document List:
Configure the Document List module template to enable KM search
If you do not need to index all the documents in the portal, you can create a search index only for documents accessed through the Document List module. This is done by configuring TREX to start indexing from a specific location in the portal.
Prerequisites
You are assigned the portal System Admin role.
You are assigned the Workspace Content Administration role.
KM and TREX are installed and configured.
NoteKM is available only for usage type Enterprise Portal (EP).
End of the note.
Procedure
Configuring the Document List for KM Search
In the portal, navigate to
Workspace Content Administration 
Module Templates 
.Select the Document List module template, and choose Edit.
In the Additional Properties tab, locate the searchEnabled property and set it to Yes.
Choose Done.
Creating a New Search Index for the Document List
In the portal, navigate to
System Administration System Configuration Knowledge Management Index Administration .Choose Create.
In the Index Administration page:
Specify an ID and a name for the index.
In the Service dropdown list, select Trex Search.
In the Items to Index dropdown list, select All.
Choose Create Index to create a new index.
Choose the Data Sources link.
Choose Add.
In the table, select workspaces.
Choose OK and save.
Note
It may take some time until the indexing is complete and you can use the search mechanism.