You can use the remote cloning method to copy a PDB from your on-premises Oracle Database 12c database to a PDB in an Oracle Database 12c database on Oracle Database Cloud Service.
On the on-premises database host, invoke SQL*Plus and close the on-premises PDB and then reopen it in READ ONLY mode.
On the Database Cloud Service compute node, execute the CREATE PLUGGABLE DATABASE command to clone the on-premises PDB.
Optionally, on the on-premises database host invoke SQL*Plus and set the on-premises PDB back to READ WRITE mode.