could you explain what are you trying to do?

would you need a link to the document shown itself? if so there is 'Item URL' common reference variable

You can use the Label control to add a hyperlink to the Form: https://community.nintex.com/t5/Nintex-for-SharePoint/Adding-a-hyperlink-to-your-Nintex-Form/td-p/83466

• In the Address field: add Item URL (in the Common tab)
• In the Hyperlink text to display field: add Name (in the Item Properties tab)

Additionally, add a Rule to Hide the Label control if it Is New Mode.