Hi there!
let me reply in your questions text:
1) I've got a magazine to sell but I would like to sell the single magazine or a year subscription. Is it possible and what have I got to do to perform this?
Yes it is, you can use quicksell business with akeeba subscription integration.
2) My PDF are very big, about 4/500 MB. Is it still possible to encrypt them?
Honestly I haven't tested with files larger than 200MB, but there is no reason why would it fail.
3) Is it possibile to encrypt them but without the block of the print? Because we are thinking to let the buyer to print some pages...
Yes, no problem.
4) If someone closes the page after paying with paypal I've heard there is however an email with a link, is it correct?
Yes, there is also my downloads section menu item type you can add to your site so people can re-download form it, or they can simply use the emailed to them links.
5) Have I got however to hide files with .htaccess to privent them to be listed on search engine?
They are already hidden by default, they can't be stolen or listed in search engines.
Let me know if you have more questions!
