What is the best way to attach photos and documents to features within a map so that you don't lose the link when the mxd is sent to another company.? I want them to be able to open the photo hyperlink without getting an error message
Use geodatabase feature attachments and then Package the whole map, creating a map package.
The map package will contain the MXD and all data necessary to display it.
It can work completely disconnected from a network or internet.