In a board view, click on an Item. The item panel will expand, click on the Add view button.
Find the app you want to embed and click on Add to item.
The embedder will be added to the item panel, displaying instructions on how to retrieve the URL of your document.
Now click on Settings, then Create New Column.
Add a Link column to the board.
Close the item panel and click the corresponding cell under the new Link column.
Now paste the URL link of your document in the dedicated text box. You can also customize the displayed text.
Click on your item to open the item panel to see the embedded document.
Done!