[HELP] For some reason when a user update his account the all pdf of user is erased?

The problem Im having is when a user fill out all of the fields, no problem the problem is when a user uploads a new pdf docs with the upload button then click submit with the button connected to the dataset on the page, for some reason it after the user save it erases all of the
pdf that was already uploaded by the user before. Why does this happen?