You won't see the category as an option if you already have an existing document of that type in your documents.
In this case, you would simply need to edit the existing one from the Document Tracking section.
To upload a new version of an existing document, select the pencil icon in the Actions column and select Upload.
The new version will overwrite the previous document. If it is not in your document tracking section, verify the archived document section and restore the document to upload the new one.