It sounds like you could use a Model
Listener for this, on the DDMFormInstanceRecordVersion.
You'd want to override the onAfterCreate method. In it
you'll need to check if the newly created form record was submitted
for the form you want to inject logic on. Then, check if the status of
the record is approved. Then, inject your business logic for creating
the PDF and sending the email.
If onAfterCreate doesn't seem to be working all the
time, you might also need to put the same logic into
onAfterUpdate. This is because the forms system has an
autosave feature, so when the user clicks submit it might either be a
create or and update in the backend.
There's a very similar discussion going on in Liferay's
community slack, by the way. Go here to join the slack worskpace
if you aren't already in there.
