Hi Steffen,
I've tried this in the past, so we could sell Address Label templates along with our other Order Printer Templates.. but never managed to create anything that was usable.
I cannot seem to find the code I was working on in the past, but here's a few things you need to keep in mind when trying to build these:
1. Order Printer only gives you access to one order at a time, so you'll need to work with and around the default styling Shopify add to each order.
2. Order Printer will put a page break after each order, so to stop it doing that and only create a page break after each 4th order, you need to override the default page break code built into Order Printer.
3. You'll need to size each label so it's EXACTLY half wide, and half high on the paper, and float each section/label to the left, so they automatically stack next to each other and flow onto new rows.
4. You will never see the layout you want on screen (as Shopify wrap each order in it's own row on screen), but when you press print your custom layout should kick in.
5. Some browsers will put a certain amount of margin at the top of printed pages, but the amount will be different on the 1st page and then any additional pages. So the 1st page might get 20mm of top margin in Firefox but then the 2nd page only gets 10mm. This makes point 3 above much more difficult.
5. Unless you always print labels in multiples of 4, you'll end up with a lot of half used label sheets. For example if you print 2 labels on a sheet, there is no way to tell it to start at label position 3 when doing you next batch.
As you can see from the above it's unfortunately not as easy as one could hope.. or maybe I'm just going about this all wrong.
It's certainly not impossible.. but I did give up when I could see that it was not something I would be happy selling for others to use.
My other app OrderlyPrint does handle this much better using a special PDF engine for address labels, in case that would be useful to you.. we support many 4 label per sheet sizes, and can continue on partially printed sheets as well.
Good luck, and I would love to see what you come up with if you go that way.
