Sharing access in Google AdWords to a Manager account is a straightforward process, but it is slightly different than sharing access to a Google Account that is not yet associated with AdWords; it doesn't require sharing your username and/or password. Take care that only the necessary level of access should be granted.

• Log in to Google AdWords (adwords.google.com)
• Select your Customer ID: xxx-xxx-xxxx (shown in the screenshot below):

• Provide the Customer ID to the person requesting access from a Manager Account.
• The Manager will then request to link accounts with your Customer ID. You will receive a notice in your account requesting to grant access. Grant access then you're done!

Revoking Access

If you need to remove a Manager Account user from your AdWords account, this can be done by:

• Navigate to Account Settings

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• Select Account access

• Selecting Terminate Access from the actions dropdown for the desired user

Conclusion

That is it. Not too painful, right?