Wake On LAN (WOL) can be used to help turn on machines that are powered off for the purpose of allowing PDQ Inventory to do a scan.
The way to set this up in PDQ Inventory is to go to File->Preferences->Scanning and then set the Offline Policy to “Wake-on-Lan then attempt to scan”
Make sure the BIOS setting on your target machines (The machine your are attempting to scan) has Wake On LAN enable or configured.
Once you have these things setup, PDQ Inventory can Wake machines that are turned off and update the scanned data.
You can watch me show you how to configure PDQ Inventory WOL settings here: http://youtu.be/w6acOmrLoOs