SendOwl

If you want to add subscriptions to your shopify you will need to be able to understand coding. I contacted help desk and they couldn't help me so I just used the paypal subscription button. Works so much easier

It looks good but it doesn't allow multiple file download.

The support was for me a horrible experience. Never had the correct answers to my questions.
Moreover if you have apps like receiptful already installed this will be complicated to setup.