Hi,
Interesting your post.
On the other hand, the double optin is especially interesting for the GDPR part, allowing you to justify that it is indeed the address of the user who made the request to be added to the newsletter. Otherwise he has little interest.
In your case, if I want to download your pdf, I just have to put a disposable email address, I validate the double in and I access this file.
Finally, if you automate the sending of pdf after the double in, the user who wants to put a fake email and access this document will be able to do so …
This is why I had previously opened a post for Wix to work on the possibility of integrating a blacklist of an email address or disposable email. But I still don’t have answers.
You can perhaps dig deeper into the subject of the “Workflow” side by creating an automation at a given stage