Create a landing page with a form, is this subscribed to a subscription list, is the information entered in the form in the text fields stored in Adobe Journey Optimizer? What happens to the information entered in the form?

@Ivan_Mironchuk  The use case is to create a campaign to be activated by API, this campaign will be the sending of a transactional email, for which I could already solve this part. In that mailing it is required to attach a .pdf file that will be the same for everyone.

When using the External Api activity in the Workflow I am getting the following XML-110009 Unable to find the element 'select' of path '' (document with schema 'dataTransferStep') error.This was working fine until a couple of days ago.

Is it possible to attach a file in an email in Adobe Journey Optimizer?, I need to activate a campaign by API and send an attachment in the email of that campaign. Is there a way to do it?