Also a previous post: https://www.odoo.com/forum/help-1/question/how-to-send-reports-directly-to-printer-in-v7-0-1341

Of course I did already, but I thought this only works to send print jobs to a printer attached to the server. How can I print on a printer attached to a client pc directly?

Use network printing (IPP). Share the printer attached to the client so that the server can see it, then attach that printer to the server. You can then send the print job to that printer connected to the client. I understand that using the said module you can only send one report (e.g. invoice) to one printer. However, AFAIK, there is no other solution yet that enables user to choose printer when printing and directly prints the invoice without download. If you are OK to get the PDF still displayed (automatically and in browser) and then user can print it (and choose the printer to print to), try the web_pdf_viewer (https://www.odoo.com/apps/trunk/web_pdf_viewer/) module. Not sure if it works with IE though.

I am absoloutly OK with having the PDF still displayed. I went ahead and installed web_pdf_viewers as you mentioned, but it does not work. I even tried to install the plugins mentioned in the app page for both chrome and firefox but no matter what I did the browser always asks to download the file. Any ideas?

We have been using that module without any problem. Check the browser's console log (Press F12 to bring up the developer's tools, there should be Console Tab) if there is any error. Not sure why it did not work in your environment.