Hi Carlos

Thanks for posting in the Lucid Community! You can't attach a file directly to a diagram or object. However you can add actions to a specific shape such as linking your shape to an external web page as explained in this Help Center article.

You can also link a diagram that you have uploaded to a web page or to another page of your Lucidchart diagram using Layers Links and Hotspots as explained in this Help Center article. 

I hope this helps! Please let me know if you have any additional questions.