Based on the issue description mentioned above, when trying to view a downloaded pdf, it shows blank pdf on your Android device, is that correct?
Could you please let us know if this happens with all the files you are trying to open?
Are you trying to download files from email or from a website?
What is the version of the Android operating system and Acrobat Reader installed on the device?
You may refer to this link for the same: Acrobat Reader Help for Android: Troubleshooting FAQs
You may also visit the following link which discusses this topic: