Syncing scorecards to a friend's phone is easy. You simply find them in your players list, and then link their UDisc Pro account by username or PDGA number. This process is explained here: Link a player on your phone to their UDisc Pro account
Note that this requires a Pro account for both you and the friend. It will not work otherwise. If your friend does not know their username, have them check the top of the Profile tab where it is listed.
Once you have linked their account, their scorecards should sync quickly. The next time they open the app, they should see all of the rounds you have scored for them added to their account and appearing in their stats pages.