It would be nice to have a 'save all closed tabs'. Then I can re-open these on the next session. Unfortunately, this option is still not available.
Google has such extension called OneTab. Something similar on Adobe Reader would be great!
This has been requested by several others (see in comments https://acrobat.uservoice.com/forums/590923-acrobat-for-windows-and-mac/suggestions/31145458-save-all-tabs-with-one-click)

Once you re-start, you should just be able to re-open the whole bunch of pdf's that you closed before with one click