I think you want to use the Content Download Program Channel and then do what Amy suggests. It sounds like you are using an Email Send Program. You can certainly put an LP, Form, and Flow in there, but probably not the best idea.
In general, you can do whatever you want in ANY program, send an email or not, but the statuses available to you will depend on the Program.
Your Program might look like:
01 Register Flow says
-If Fills Out Form on Page Y
-Do XYZ like Change Program Status to "Downloaded"