I have created a feedback file containing generally guidelines which each student needs to receive upon uploading their assignment. At the moment if you select the feedback option as "feedback file" you have to upload a file for each student. How can I set this up so that I upload the file once, but it is only sent out to a student once they have uploaded their own assignment?
Could you use the activity completion and restrict access settings to make the feedback file available?
Set the assignment activity completion to "Student must submit to this activity to complete it".
Then put the feedback file in as a resource in Moodle. Set that file to restrict access to students who complete the activity (submit it). You could even keep it hidden until students meet the restriction (it's greyed out by default).
It will automatically show up for students, but won't be "sent" to them--they'd have to click on it.
I'd also indent the resource in the topic block so it appears subordinate to the activity.
I can't think of any other way to do what you want automatically. Maybe someone else can.