1. Make sure that you have the Search Index schedule task enabled. You may also check to see whether the index file is changed or not.
2. Use below tools to open attachment in the OS that runs Kooboo. If you can read text out of the files, that means ifilter is installed correctly.
File Attachment(s):

IFilterTester.zip
(24kb) downloaded 5 time(s).You cannot view/download attachments. Try to login or register.
Regards,
Jifeng Huang
Kooboo Team
Microsoft ASP.NET MVP