How do I edit the organization's contact information on an invoice automatically generated when a person signs up for a CiviEvent and chooses to Pay Later (also for event registration confirmation)? The invoice was created by a developer the organization no longer uses, and the organization's address and phone have changed. We currently have Joomla 3.3.1 and CiviCRM 4.4.5
If the organization's information in its Civi contact record is correct, then the next place I would look would be in the message templates (Administer > Communications > Message Templates, the templates for receipts are under System Workflow Messages). You should be able to locate the information in those with a find - if you are not familiar with Smarty, however, be careful not to modify the code around the information as you might inadvertently break the template. (It's probably a good idea to save the version currently in use before you start modifying, just in case you need to step back.)
Hope this helps, Lesley
In addition to what Lesley said, you may want to consider updating CiviCRM to Version 4.6.x as it has a nice built-in invoice feature.
As it is a customization (and prpobably no one knows how it works in detail?), if you cannot find the template under workflow messages it may be a good idea to upgrade instead of trying to fix the custom function.