The calendar in question is a standard-size printable calendar, which you must be able to find in any office supply shop. You will want to download the calendar onto your computer first, then move it to your hard drive.
When you have actually conserved the calendar onto your computer, it will need to be converted into a PDF format. Simply search for the appropriate file type, then follow the on-screen guidelines to conserve it as a PDF. It is extremely likely that October 2021 will be providing many various templates.
Image source: 2021calendarsprintable.com