How do I share multiple files at once?

It appears that the basic functionality like that isn't implemented at the moment outside of manually sharing? Not sure why since multi file sharing/folder sharing has been around for a few decades now but I am sure there is a logical reason.

As I see it,you can't do it without subscription.

Yes, you can select and send/share multiple files at once.

Start at https://cloud.acrobat.com/send. Click on Select Files to Send, and then follow the instructions for selecting files. If you want to add even more files, simply click on Add Files:

You can include up to 50 files per 'transaction.'