Firstly, you can open the Notes document that you would like to copy. Then you can follow the steps to obtain the document link as below
1.    Select [File] > [Properties]
2.    Select [Document] > [<+>]
3.    Copy the value of Identifier
4.    Paste the link on your email with Outlook, e.g. Notes://UM2/48256D2100248775/C4CE5EEF86962C1E48257AF…….48257E7D0030846D

Document Propertics

Remark: Besides above workaround, you can still using your Lotus Notes email account to send an email with document links.