For example a birth certificate that references the child and the parents. I have uploaded it to the child, but would like it to show on the parents media tab as well. Is there a way to do with without uploading 3 separate copies of it?
Yes. When you upload media, you first create a media object which contains the filename along with media type and title. This object can then be linked to multiple individuals. However, I usually create a source and put the text in the source, then link the media object to the source. The source is what gets directly linked to facts on individuals or families.
But...’nwagers’ is right. The correct was to use a source type media is as a reference within a SOURce then connect the events/facts of the individual that references that source via a source-citation.