Why does Print from a WebView return a blank page?

Question

I have an Android WebView contain order mobile web app (asp.net)

Everything is fine except for when I open a pdf file :

 

string UrlForAndroid = "HTTPS://docs.google.com/gview?embedded=true&url="+openurl;

this.Page.Response.Redirect(UrlForAndroid, true);

this.Page.Response.End();

 

 

It opens but when I try to print it, it returns a blank page, even when I press share.

However, I've already set access read & write to external