I have a spreadsheet that I track everything on. A few nights ago I googled something along the lines of XXXX med application "update" and looked at each of the applicant portals so that I could make a note about it. Like the other poster said, sometimes there is no place to upload updates. That is probably a hint that they do not accept them. Sometimes schools say they do not accept updates pre-interview. Other times, they don't say anything. I'm sure it is fine to upload updates as long as they do not explicitly say not to, but just be aware that they have no obligation to actually read the update.