Ive been setting up a Sharepoint demo and found the following useful iFilters for PDF and ONE files.
If you want to search through the content in PDF files using Sharepoint, the iFilter at http://www.adobe.com/support/downloads/detail.jsp?ftpID=2611 would do the trick. You would need to add PDF as a file type to be included in the content index for Sharepoint.
To search OneNote docs, Install OneNote 2003 on the computer that is running Windows SharePoint Services. The iFilter for OneNote 2003 is installed when you install OneNote 2003 on the computer. You would need to add ONE as a file type to be included in the content index for Sharepoint.