The seal goes on the inside envelope. Handwrite the inside envelope as well as the outside address. Labels are tacky. You are not a charitable foundation soliciting donations. You are a graduate inviting personal friends and family to a special event.
The seal goes on the inside envelope. The outside envelope is for mailing only. Y]The inner envelope is for show. I would handwrite the inside envelopes.
On graduation announcements, it is standard to put the seal on the outside envelope. And yes, on the inside envelopes you should write out the addresses.
