You can use the web-view component and it works for some document types. Or the external link action which can be found when adding a new action > Link > Website in the bottom. I remember cosmith.io (@gskachkov) have a document viewer which can be used too. What type of documents are we talking here?
If you’re willing to pay, you could hire an expert from the experts page. : Hire an Adalo Expert | Adalo
Or you can post a job request in this forum under the Jobs / Freelance category.