PDF files posted in my google drive are not opening showing the number of pages with blank content

[Swarat5C3F]

I am using win 10 pro with 6 GB RAM on intel core i3-5005U CPU. My acrobat reader DC is release 2015 version 2015.023.20070.

Recently i managed to get few scanned PDF files in my google drive where i created a dropbox. Now when i have downloaded all these files in my laptop C: drive, none of them are opening. They are just showing 4 pages and the entire file is blank.

Whereas few files which i have received through e-mail works fine,

Please suggest.

[try67]

These files are corrupt.

[Swarat5C3F]

I have received these files from my students staying at different locations and using different devices. How come all 45 files are corrupt?