There is nothing to prevent you from working while also receiving a monthly pension. The amount of pension you receive won't change.
There is no minimum amount of time required between starting your pension and re-entering the workforce; however, you must have terminated your previous employment to begin drawing your pension.
It's important to remember that you can't receive a PSPP pension and contribute to PSPP or the Management Employees Pension Plan (MEPP) at the same time. If you start a new job with a PSPP or MEPP employer, you must let your employer know that you're a PSPP pensioner and can't contribute to either of those plans. Your prospective employer's Human Resources area can help if you have questions.
More on PSPP employers