I want people to be able to give their email id to be get a free pdf and then send them a series of emails automatically. After that they should receive our bi-monthly newsletter. Which is the best app for this?
This is PageFly - a Free Landing Page Builder for more than 80000 Shopify merchants, I would love to provide a solution to your question.
Increase engagement with customers is very important, and sending a monthly newsletter is also a good method. I highly recommend MailChimp - how to create a newsletter with MailChimp. You can give it a try.
Especially, PageFly integrates with MailChimp, you can not only build a beautiful, high-converting store with PageFly but also use the MailChimp Form element to collect customer's emails and send them newsletters/ emails
Let me know if you have any further questions. Like my answer, if you find it helpful.