Here's the scenario I run into every couple of weeks:

I shut down the computer/it crashes/power is turned off. I happened to have 20+ PDF documents open, most downloaded from the net and sitting nicely in /tmp.

On reboot, /tmp gets cleared. Session starts and up pop 20+ evince windows most telling me they were "Unable to open document". To which my obvious question is: what document?  This is highly frustrating.  I think evince should tell me what the document is, so that I can find it again.  Sometimes I've even saved a copy, but it doesn't matter if I can't remember what it was.

Below is a one-line patch adding the URI to the message.  It is relative to 3.4.0 but the bug's been there for over five years, and the details of the patch are not really important.

--- evince-3.4.0/shell/ev-window.c	2012-02-22 06:12:16.000000000 +1100
+++ evince-3.4.0local/shell/ev-window.c	2012-08-29 15:33:43.000000000 +1000
@@ -1728,7 +1728,7 @@
 		ev_password_view_ask_password (EV_PASSWORD_VIEW (ev_window->priv->password_view));
 	} else {
 		ev_window_error_message (ev_window, job->error, 
-					 "%s", _("Unable to open document"));
+					 "%s: %s", _("Unable to open document"), job_load->uri);
 		ev_window_clear_load_job (ev_window);
 	}	
 }