Documents Metadata, Knowledge Structure

We are publishing all the papers from the Hypertext Conference 1987 with Hypermedia Communications. I want to add as Keywords (or Tags) some information such as year, author, keywords, and Conference. How should I do it?
There are two aspects to consider in Metadata. On the one hand, how to add the metadata that will create a knowledge structure. On the other hand, should be easy to use the system to create personalized metadata and knowledge structures.

Alternatives to add Metadata to a document

1.
Create customizable metadata fields on the document, as in Tiddly Wiki.
2.
Create Hashtags as Document Titles and add them as links to the document. You will access the Documents through a powerful backlinks list, as in Roam Research.
3.
Create a Hierarchical Tags System as in Bear.
4.
Create Claims as external Messages.

Alternatives to add Personalized Metadata or Knowledge Structures

1.
User versions with different Metadata or Tags per Author or Group.
2.
Use Claims.
3.
Use Hashtags as Document Titles.