Overview:

The user sets a File Extention as a URL, but encounters the error: Download failed when downloading the file in the Document tab of CRM iPad.

Root Cause:

This should be supported based on Documents and Attachments.

An administrator can reference a URL to a file rather than upload the actual file when creating a new document record. The file from the URL location is downloaded to the device when offline and downloadurl displays in the Keywords field. Be sure to separate the keywords with a comma. Externally sourced files behave the same as normal files on the device.

But the file only has offline in the Keywords field. 

Solution: