Magda Sicknick

<ul>
<li>Redirects attachment pages to the parent post, or home page if no parent post exists. </li>
<li>Hides permalinks when editing/uploading attachments. </li>
<li>Disables ‘Link to’ option when inserting media to a post/page.</li>
</ul>

WP Disable Attachment Pages

Redirects attachment pages to the parent post, or home page if no parent post exists.

ryanpcmcquen

Makes local copies of all the linked images and pdfs in a post, adding them as gallery attachments.
Source & support:
https://github.com/ryanpcmcquen/import-external-attachments
<h4>Credits</h4>
This plugin is based on the work done in the “Import External Images” plugin by MartyThornley.
https://github.com/MartyThornley
HTTPS support added by IvanDoomer: 
https://github.com/IvanDoomer
PDF support added by bengreeley: 
https://github.com/bengreeley
Most of the JavaScript was rewritten from the original plugin, to reduce the 
number of global variables.

Import external attachments

Makes local copies of all the linked images and pdfs in a post, adding them as gallery attachments.

WP Disable Attachment Pages vs Import external attachments