You are searching in CQ5 for text contained within assets like PDF & Word documents in DAM, and not getting any results.
This issue is resolved in CQ5.5 SP1 and SP2 and later versions. You should download these updates from PackageShare and update your CQ instance.
After updating CQ new documents in DAM will be indexed, but the existing documents will not. Perhaps this is acceptable if you are just setting up a new instance, and do not have any existing documents that you need indexed.
To get existing documents indexed, you will have to re-build the lucene index as follows:
 Open http://<host>:<port>/system/console/bundles
 Find the ID for the following bundles
- Apache PDFBox (org.apache.pdfbox)
- Apache Tika core (org.apache.tika.core)
- Apache Tika parsers (org.apache.tika.parsers)
 Look into crx-quickstart/launchpad/felix for the folders corresponding to the 3 IDs in :
 For each bundle in , change the value in the bundle.startlevel from 15 to 14
 Restart CQ and check in the Felix console that the 3 bundles has the start level set to 14.
 Stop CQ
 Delete crx-quickstart/repository/workspaces/crx.default/index folder
 Restart CQ and wait for the indexing to complete