We don't host the content files.
So you should upload your media like images, pdf etc on your own hosting or on cloud storage like OneDrive, DropBox, Box.
Here is an example of adding image and pdf in a web view.
First upload your image in preferably public folder.
Than, click on image details and embed the image
Than copy the image link, you can also change image size.
In Mobidonia, inside the webview add the image
Save it. For source feed, use "From Content"
That is all.
Upload your pdf in public folder, and click on it to embed
Copy the generated HTML Code
In Mobidonia, in the web view in the "Source" tab add the copied HTML embed script
Important: in the <iframe code for width and height use 100%