@Jinfei Zhu
Databricks now uses accredible platform to issue you badges and certificate. You can login to accredible platform (https://v2.accounts.accredible.com/login) or create one if not already done using the same email id used to complete your Databricks Accreditation.
Once your are logged in all of your Databricks credentials will be visible and PDF can be downloded for each of them