Print format when using Windowed Envelopes

Here in Switzerland and Germany Windowed Envelopes [1] are quite common. How would I adjust the print format to have the address always in the right place and maybe even the sender’s address in small letters above it, like in the following example: Briefkopf Vorlage & Muster: Briefkopf selbst erstellen – Vorlagen & Muster

[1] Windowed envelope - Wikipedia

You can use absolute position in HTML and use metric units like top: 3cm for your block elements etc.

Thank you!

So I create a custom print format – one for every document, as I understand. I probably have to check the “custom format” checkbox and then declare everything in the HTML format, right?

One thing I could not find out was how to get the address of the client in the print format. The following did not work:
{{ doc.address}} or {{ doc.get_formatted("address") }}

Additional question:
Is there a possibility to consolidate this into one print format? Because the top bit of my documents with the address of the client is always the same.

You can try adding this to letterhead.

The field names are from the form. I use the customize form feature to look at the fields to get the field name in the database to use the {{ doc.* }} format. This might help you.

If you get this figured out, would you mind posting results w/ code back here? We have same need in the US for our payroll and other checks.