Found the solution to my Print Spooler error after Windows 10 upgrade: "Windows could not start the Print Spooler service on the local computer. Error 1068: The dependency service or group failed to start." 

Thanks to http://www.registryrecycler.com/blog/2013/12/how-to-fix-printing-error-in-windows-8-1/ for the fix. Apparently some Windows 8.1 upgrades had the same problem.

A registry change is required. Make sure you have a Registry backup before making changes.  

• Press Windows key + R on your keyboard to open the Run box.
• Type regedit in the Run box and hit Enter to open Registry Editor.
• Confirm the UAC message by clicking the Yes button.
• In the left pane of Registry Editor, expand HKEY_LOCAL_MACHINE to find the key below.
• SYSTEM\CurrentControlSet\Services\Spooler.
• While the Spooler key is highlighted, navigate the right pane to allocate the value DependOnService.
• Double click this String value to Modify the data within.
• The value data field should contain the text saying RPCSS, followed by http in the next line.
• Select and delete the letters http and click OK button to save your changes.
• Leave the RPCSS part of the value data as it is written.
• Close Windows registry and Restart your computer.