Can´t access some pdf files via files on my Ipad

I want to work on some pdf on my Ipad. Therefore I places these files in a cloud.

This works usually fine, but sometimes I receive this error:

"Your device couldn´t connect to the server. There may be a problem with the server or network"

However all other files in the same (cloud) folder can be downloaded and opened. It seems there is someting strange with this pdf?

(This pdf opens normal on iMac with preview or adobe)