PDF仅在Android手机上“下载不成功”

I know similar questions have been asked, but none of them were answered. As the heading suggests, a PDF document is successfully retrieved on PC as well as iPhones from the URL (URL calls the controller of a C# Web API and the function returns a PDF in HttpWebResponse), but as soon as it comes to Android phones, it says "Download Unsuccessful", unless the link is opened in Opera.I know similar questions have been asked, but n