"standard input" means that the file has been taken from the standard input (stdin) stream passed to lpq (or cupsd or whatever).
It's basically a default name used when the printing program doesn't bother to tell the print server what the job is called.
Sometimes you can just tell by the size of the print job.
You can fix this on the client side by using, for example,
as the print command instead of
. How to change this depends on the software being used; sometimes you may have to edit code (or petition the writers of the program) to put a document name on the print job.
You can see which documents are printing by looking in the appropriate place under /var/spool. For example, under CUPS, you will have a directory /var/spool/cups containing files like (for instance) d000ID
-001. If you open these files with gv (in an X windows terminal)
it will show you what the contents of the file being printed are (assuming it's been converted to PostScript, which is usually the case).
Hope that helps,
— Robert J. Lee