Hello Rachnan,
We're sorry for the delayed response and inconvenience caused. As per the description, you are not able to open PDF files, Is that correct?
Please reboot the machine once and open any PDF file. Navigate to Window>Cascade>Tile in Adobe Reader and try opening few PDF files and see if this brings up the PDFs?
Also, check for any pending updates of Adobe Reader from help>check for updates, reboot the machine after updating Reader.
If you are using Windows machine, repair Adobe Reader from help>repair installation and reboot the machine after repair. You can also refer and try the suggestions from the following Adobe article Can't open PDF
Is it a Mac or Windows machine and what is the version of OS installed? What is the 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.