You don't need turn off highlighter, but you need to switch off highlighting. >From the menu view switch off "Syntax" or use toolbar button. When syntax highlighting is off, you will see active URL links.
Another possibility in all case is select URL and use right mouse (context menu) and Open selected file in default application. -- <http://forum.pspad.com/read.php?2,59935,59936> PSPad freeware editor http://www.pspad.com
