ostlund

This plugin lets you insert a upload form on your pages so visitors can upload files to a Dropbox account.

Dropbox Upload Form

Inserts a upload form for visitors to upload files to a Dropbox account

minnur

Import files from or create external links from third-party services into WordPress Media Library (Dropbox, Box, OneDrive, Google Drive and any other external file from URL).
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<a href="https://downloads.minnur.com/wordpress/external-media-premium" rel="nofollow ugc">External Media Premium</a> is a premium version of this plugin with support for Unsplash, Instagram, Pexels, Pixabay and AWS.
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This plugin provides convenient way of linking and using files from the services listed above. It is intuitive, controls located where you expect them to be. For instance if you would like to create a link to your file in your Dropbox account, just press Add Media and choose Insert from URL media tab and then click Link to Dropbox button.
The plugin provide two options: 
– Insert from URL (this will link to a file located on one of the services) 
– Import file (this will upload a file from a remote service and store the file in WordPress)
Note: Imported files from a remote services become a permanent file and changes made to the file on the service won’t reflect on the site. You would have to re-import the file using External Media plugin.
The plugin won’t upload the same file twice, instead it will check if the file already exists in your WordPress site and re-use it.

External Media

Import files from thrid-party services into Wordpress Media Library (Dropbox, Box, OneDrive, Google Drive, and any external file).

Dropbox Upload Form vs External Media