Hi @Daniel Finch8! I'm not clear on why you would want to attach a landing page and send it to people who are already subscribed... can you clarify what end goal you're trying to achieve so we can try to help?
A landing page is a place where you collect emails from new subscribers who aren't on your list yet. You can use this landing page on your own website, or use the URL Convertkit generates for you.
Convertkit doesn't do attachments. "Attachments" are actually just links. When things are physically attached to an email (such as a PDF) it is often flagged as suspicious. To avoid that, the link to the attachment is included instead of the actual attachment.