How to share a file as a link from iCloud Drive:

1. Long press on file in doc browser
2. Share > Add People > Share Options
3. Select ‘Anyone with the link’ and ‘View only’
4. Go back, select Mail, email to yourself
5. Long press on file in email
6. Select Copy Link, paste where you want

This is slightly easier if you rely on having a 3rd party app installed. E.g. you can ‘Share’ to Bear or OmniFocus and then copy the link from the share extension compose sheet.