Mobile print is not set up to print multiple copies of the same file.
To work around this, save the same file under different filenames (i.e., File, File1, File2, File3, etc.) and attach those to the email you send to mobile print. This will, in essence, print multiple copies of your print job.
You may also use the copier function of the printer to produce multiple copies of your print job. Ask a service desk assistance for help in setting this up.