I have few question about DIDs and DID document

i might be better not to say here because here is not for decentraized identity foundation community ,but i couldnt find any for those discussion forums so that i decided to ask close community here.

so i have 3 questions
1 Who should create a DID document, is it possible that some random person create a DID document for someone ?
also how is the DID document created exactly?

2 If i want to upload DID documents in some distributed ledger system, is it possible?
and if i could , the document has to be crypted ?

3 which is issued first, DIDs or DID document ?