Get "document" URL

Hi,

I would like to get the custom field associated to the document creation link. Please find below the screenshot from the link i’d like to get. “document”

Then, i want to put this link in an automated email, in order to send quotes to my clients and to offer opportunity to sign it.
For example :
Hello {{firstname}},
Please find here the link to access to your quote: {{document-link}}
Best,

Is anyone knows how to get this custom field?

Many thanks

François