Hi Manuela,
We're sorry for the delayed response and inconvenience caused. Please create a test user profile with full admin rights and check.
Is any Group policy is applied which is getting refreshed after some time? Is any security software installed and what is the version?
What is the current dot version of Adobe Reader installed? To identify refer to Identify the product and its version for Acrobat and Reader DC
Let us know how it goes and share your observation.
Thanks,
Anand Sri.
Hello Anand,
user with full Admin rights is able to open more than one pdf from Explorer in a new tab.
Version is 2018.011.20058
We have no GPO for Adobe.
Thanks for your help!
Best Regards
Manuela