Office 365 and SSO questions

Office 365 and implementing SSO to a system already in place.
So 2012 AD on prem and i want to sync it to Office 365 using the Azure AD Connect system. Only want passwords synced.

above link shows how to set it up from scratch, shows all the on prem users been added to Azure AD. I already have my users in place in 365, im assuming when i set the sync going it will add all the users from onprem to Azure AD also.
Im looking at duplicate Azure AD users then in the 365 portal?
Can i get it to sync with the current setup, link on prem to the users already setup in Office 365 Azure AD?
if so how do i go about it

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Vasil Michev (MVP)Commented:
If you already have the user accounts provisioned in O365, you will have to "match" them against the on-premises ones in order to avoid duplicates. You have two options:

1) Soft match as detailed here:
2) Hard match as detailed here:

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Saurabh YadavMCPCommented:
In order to avoid to duplicates you can follow the below mentioned options:

1. Soft match:

2. Hard match:
SoHandyAuthor Commented:
Ta mate
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