Can I add a primary key automatically for all tables?

Question

I have a database (postgresql) with 10 schema and every schema has 10 tables. For some reasons, some tables do not have a primary key.

Is it possible to create a function/trigger that can look for all tables and

• add a column id_pk serial (if the column does not exist)
• and make it a primary key (if the table has not any primary key)?