A paper calendar can’t be shared unless it is always posted in a public place. However, if you post it, you can’t carry it with you. So, a shared paper calendar must be synchronized with personal calendars every day. Just copy over new appointments or changes each morning during daily review, and never add shared calendar appointments for the current day. Otherwise, your calendars will not agree.
If you decide to do this, add this step now to your list of steps for your daily review.