How do I find the "ID" of my Dropbox Paper Doc?

First, note that there are currently two different Paper configurations that an account may be using, which will affect how you use the API to interact with Paper docs. You can find information on this in the Paper Migration Guide.

For legacy Paper docs, you would use the /2/paper/docs/list and /2/paper/docs/list/continue endpoints to get a list of the account's Paper doc IDs. You would use /2/paper/docs/download to get the information for any particular Paper doc. In the official Dropbox Python SDK, those are paper_docs_list, paper_docs_list_continue, and paper_docs_download, respectively.

For Paper docs as files in the filesystem, you can use the standard files endpoints to get information about the Paper doc files. You can use /2/files/list_folder and /2/files/list_folder/continue to list the contents of any folder, /2/files/get_metadata to get the metadata for any particular item, and /2/files/export to export the data for any particular Paper file. In the official Dropbox Python SDK, those are files_list_folder, files_list_folder_continue, files_get_metadata, and files_export, respectively.