Qarib Haider

This plugin adds a QR Code for each post (link) published on the site. The plugin support all the registered built-in and custom post types, along with pages, this can be changed under the settings page of the plugin.
<h3>Settings</h3>
Following are the available configurable options in the plugin
 Option 
 Default Value
 Size 
 300 pixels
 Margin 
 20 pixels
 Image Type 
 PNG
 Post Types 
 [All Available Post Types]

Link QR Code

Add a QR code to each post, page and custom post type

Elias Lackner

Upload Directory Cleaner scans through your WordPress upload directory searching for all files not being registered in your Media Library. After the scan, choose which files to delete from the list showing all unregistered files.
Features:
<ul>
<li>Archive Directory</li>
<li>Scan Directory (Settings: Exclude top-level directories and files from the scan or add custom ignore strings.)</li>
<li>Delete Files (Settings: Keep Thumbnails, Delete Empty Directories)</li>
</ul>

Upload Directory Cleaner

The UDC plugin allows you to scan and delete all unregistered files from your Wordpress upload directory.

Link QR Code vs Upload Directory Cleaner