You can now add file links in the User Forms builder:
https://user-forms.wrk.com/builder
Alternatively, you can add the following HTML:
<wrk-file-link file='{{Replace with file Data Library Item}}'>Download file</wrk-file-link>
The file reference is converted into a signed download link when the page opens. A fresh link is generated each time, so users can continue accessing the file without encountering an expired link.