Hi there,
Thanks for reaching out. This feature is not available in Illustrator on the iPad yet. However, we're working on it. I'd request that if you could take out a moment and post this as a feature request here: https://illustrator.uservoice.com/. This way, you will keep getting all the updates related to this feature & other users can also upvote, which would help us prioritize.
In the meanwhile, the document from iPad syncs automatically to the desktop, so you can use the desktop Ai to manage your export settings.
Regards,
Srishti