Organisations need to file various reports to various regulators at various times. Sometimes data prepared for one report needs to be submitted subsequently as part of another report.
Example: The annual financial report is produced in January and submitted to a particular national regulator. A different report is required about sustainability and due in April but is expected to include metrics around Revenue, that need to come from the last published financial report.
Traditionally, a later report will include a footnote or similar acknowledging where a given fact originated and a link to viewing the original report.
In digital reporting, the requirement is for the link to be easy to author and easy to follow by interested parties such as auditors, regulators and consumers.
Example
The simplest link is an HTML hyperlink. In the below screenshot, “2020 financial accounts” is a link to a different document.

Links
Inline Viewer – XBRL International Inc. Sustainability Disclosure