I have two adjacent iMacs and wish to copy my documents folder from one to the other?

How big is your Document folder?

If it is small, you can use File Sharing over your local network.

If it is large, you would be better off using a Flash Drive to move it from one Mac to the other.

If both computers meet the following minimum requirements AirDrop is another option.

• Both devices are within 30 feet (9 meters) of each other and have Wi-Fi and Bluetooth turned on.
• Each Mac was introduced in 2012 or later (excluding the 2012 Mac Pro) and is using OS X Yosemite or later. To find out, choose Apple menu  > About This Mac. 
• Each iPhone, iPad, or iPod touch is using iOS 7 or later, with Personal Hotspot turned off.

Make sure that your devices can receive AirDrop requests:

• Choose Go > AirDrop from the menu bar in the Finder, then check the ”Allow me to be discovered by” setting in the AirDrop window. iPhone, iPad, and iPod touch have a similar setting. If set to receive from Contacts Only, both devices must be signed in to iCloud, and the email address or phone number associated with the sender's Apple ID must be in the Contacts app of the receiving device.
• The Contacts Only option is available on devices that support iOS 10 and later, iPadOS, and macOS Sierra 10.12 and later. If AirDrop is set to Contacts Only on a device with an earlier software version, you can change the option to Everyone while using AirDrop, then change it back when not in use.
• Choose Apple menu  > System Preferences, then click Security & Privacy. Click the Firewall tab, then click the lock  and enter your administrator password when prompted. Click Firewall Options, then deselect “Block all incoming connections.”