If your client cannot view their documents on an iPad, ask them to try the suggestions below.
Ask them to try opening the document in a different browser on the iPad, such as Chrome instead of Safari.
Their iPad or software version may be outdated. Ask them to check for updates, install any available updates and try viewing the document again. They can also retry with another browser.
If the document still will not open, ask the client to try a different device such as a smartphone, laptop or desktop. If it works on another device, the issue is specific to the iPad.