A friend of mine owns a document from 1913 signed by Tsar Ferdinand I of Bulgaria( https://en.m.wikipedia.org/wiki/Ferdinand_I_of_Bulgaria). It belonged to his grand grandfather to signify his outstanding military accomplishments.
At least here in Bulgaria that has some somewhat significant historical value, but I am worried about the way it is preserved.
Currently the page is laminated and in a picture frame (not tightly sealed), but dark spots have appeared on the page.
What would be the best way to go about preserving this document?
I might be able to provide pictures a bit later as well, but am not 100% certain as I am travelling and will leave fairly soon.
Might be worth to note that it's unlikely my friend will be willing to give the document to a museum/exhibition as it has strong sentimental value to him.
(this is a cross post from r/AskReddit since my post there was deleted – no additional text allowed apparently)
Edit: I was unable to get pictures but it seems that no one noticed this post so it doesn't matter… And I'm now basically talking to myself.. Hmmmm
Source: reddit post