Same way a passport is, I guess? 99% of organisations that ask for a passport image have no way of knowing whether it is fake or not, a letterhead is slightly easier to mock up though.
The PRADO website says it is not (yet) fit for purpose and you should go to your own country's agency to verify passports. The fact of the matter is that for most EU countries, you simply cannot verify them unless you are a government agency. I have had to figure out ways around this professionally, so I am reasonably certain this is accurate (at least up to a year or two ago).
Passports have verifiable codes on them. Letterheads can be copied like word docs.
Granted that's not to say people will actually verify passports using the data, but it is there compared to a letterhead being effectively just a random doc template.
I'm in the UK. If you give me a passport as ID I have no way of knowing if it is genuine. If you present a company letterhead I can, at least, check the company exists, verify your name is the same as a registered director and also see some basic financial history.
and we have a central organisation called PRADO with information on how to verify any EU country's passport. https://www.consilium.europa.eu/prado/en/prado-start-page.ht...