I have an idea to avoid the hassles of getting the permissions changed. Move the /Library/WebServer/Documents to you home folder. Use the unix ln command to redirect input to your version of /Library/WebServer/Documents .
mac $ pwd
/Library/WebServer
mac $ ls
CGI-Executables/ Documents/ share/
mac $ sudo mv Documents/ /Users/mac/Documents
mac $ ls -l /Users/mac/Documents/Documents/
total 72
-rw-r--r-- 1 root wheel 3.6K Sep 9 2014 PoweredByMacOSX.gif
-rw-r--r-- 1 root wheel 31K Sep 9 2014 PoweredByMacOSXLarge.gif
-rw-r--r-- 1 root wheel 45B Jun 11 2007 index.html.en
mac $
mac $ sudo ln -s /Users/mac/Documents/Documents Documents
mac $ pwd
/Library/WebServer
mac $ ls -l
total 8
drwxr-xr-x 4 root wheel 136B Sep 9 2014 CGI-Executables/
lrwxr-xr-x 1 root wheel 30B Dec 10 16:31 Documents@ -> /Users/mac/Documents/Documents
drwxr-xr-x 3 root wheel 102B Sep 9 2014 share/
mac $
mac $ ls -H /Library/WebServer/Documents
PoweredByMacOSX.gif PoweredByMacOSXLarge.gif index.html.en
mac $ ls /Library/WebServer/Documents
PoweredByMacOSX.gif PoweredByMacOSXLarge.gif index.html.en