Currently there is no way. I have searched for a solution and did not found anything but nevertheless it is possible to do that. You could parse the item files of your job, they contains everything whats needed.
At the moment I "paint" it also for my self, also because of the necessary tidy up of the picture.
I have made my documentation with the yEd editor. This is a graphml editor and therefore very capable to documenting sources and targets of a job and the job chain it self.
http://www.yworks.com/en/products_yed_about.html
For a database ERD diagram you could try the Oracle SQLDeveloper. This program is free and works also for other databases and can create ERD diagrams (also from an existing database)
