China is a society where official seals are still in use everywhere, not only by officials but also by individual people. What do you do if you are a foreigner and your documents aren't affixed with these things? Certain people are likely to doubt the validity of your documents! What do you do?
You get them affixed anyway.
When I went to do my fieldwork in China, I was required to bring a chest x-ray of myself, but it had to be an official one. To make it official, I had the x-ray embossed repeatedly with an embosser from the hospital, and also affixed with paper stickers on which several address-stamps were stamped in blue or black, and over which various hospital employees - whoever happened to be around - signed their names. (No red ink for the signatures, of course, as it is considered a bad thing in China — funny, considering that "red ink" is an English metonymy for bureaucratic fuss.) That seemed to do the trick. As someone later said, it still wasn't an official Chinese x-ray, but it looked far more serious than what the other foreigners in Fúzhōu that year had brought. Some of them, as I recall, were required to have new x-rays taken there; I was not.
I also brought a copy of our marriage license, which in New York at that time was just a flimsy scrap of photocopy paper, hard to read and yellowing. It had come embossed with a seal and stamped with a multicolored stamp that contained a facsimile of the County Clerk of New York County at the time we were married. But I was warned that it would not be recognized by the Chinese government. So I had it re-certified by the County Clerk's office, adding another layer of paper bearing the actual signature of the current County Clerk, and that allowed me to get a certificate from the office of the Secretary of State of New York State attesting to the authenticity of that signature. The latter certificate was sufficient to be recognized by the Consulate of the People's Republic of China, which affixed its own certificate, attesting to the authenticity of the signature of the Deputy Secretary of State of New York State. The Chinese certificate was signed by a consular official and stamped with a red seal. The whole pile of papers was stamped with an embosser. None of the three certifying documents said anything about the original being a marriage certificate – they merely testified to the authenticity of the signature of the official on the previous document. I carried this little set of papers with me during all our travels to China, over many years.
We only had to use the marriage certificate once or twice — once when introducing ourselves to the local officials who sponsored me after my academic sponsor abandoned me, and once when checking into an official guesthouse in another city and asked to prove that we were married. My wife, however, being a Taiwanese compatriot (albeit traveling on a US passport), was not required to have an x-ray at all, even though she came to all the same places I did and stayed for the same length of time.