SharePoint – Access Denied When Enabling The Office SharePoint ServerPublishing Infrastructure,Site Collection Feature

Cause:
The application pool account does not have access to create / update timer jobs which is required when enabling the Office SharePoint Server Publishing Infrastructure Site Collection feature.
Solution:
There are two options:

1. Temporarily add the application pool account to the farm administrators group, or
2. Run the following command:
   stsadm -o activatefeature -name PublishingResources -url http://SITECOLLECTIONURL

Steps to add application pool account to the farms administrator group

1. Start > Programs > Administrative Tools > IIS Manager
2. Expand the Application Pools node, locate the application pool associated with the site collection that is experiencing an issue
3. Right-Click the Application Pool and select "Properties"
4. Select the "Identity" tab
5.  Note the user account
6. Start > Programs > Microsoft Office Server > SharePoint 3.0 Central Administration
7.  Site Actions > Site Settings > Advanced Permissions
8. Click "Groups"
9.  Click "Farm Administrators"
10. New > Add Users
11. Add Users: Type the name of the Application Pool Identity account
12. Give Permission: Add users to a SharePoint group: Farm Administrators
13. Add the Application Pool account to the Farm Administrators group
14.  Send E-Mail: Uncheck (you most likely do not want to send an email)
15.  Click OK
16. Try again to activate the "Office SharePoint Server Publishing Infrastructure" Site Collection Feature