ChrisHurst

MyWebsiteAdvisor

This plugin allows you to watermark your previously uploaded images using a PNG image file with transparency as well as text signature. 
The user friendly settings page allows for control over the appearance of your watermark. 
You can set your watermarks to always be a specific percentage of the target image. 
This plugin will add the watermarks to ALL of the images in your WordPress uploads directory.
Please BACK UP all of your uploads via FTP before using this plugin!
<a href="http://mywebsiteadvisor.com/plugins/bulk-watermark/" rel="nofollow ugc">Upgrade to Bulk Watermark Ultra</a> for advanced 
watermark features including:
<ul>
<li>Fully Adjustable Text and Image Watermark Positions</li>
<li>Adjustable JPEG Image Output Quality</li>
<li>Highest Quality Watermarks using Image Re-sampling rather than Re-sizing</li>
<li>Lifetime Priority Support and Update License</li>
</ul>
Check out the <a href="http://www.youtube.com/watch?v=XkFXBjfzw2I&hd=1" rel="nofollow ugc">Bulk Watermark Plugin for WordPress Video Tutorial</a>:
<iframe loading="lazy" title="Bulk Watermark for WordPress Tutorial" width="750" height="422" src="https://www.youtube.com/embed/XkFXBjfzw2I?feature=oembed" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>
Developer Website: http://MyWebsiteAdvisor.com/
Plugin Support: http://MyWebsiteAdvisor.com/support/
Plugin Page: http://mywebsiteadvisor.com/plugins/bulk-watermark/
Compare Watermark Plugins: http://MyWebsiteAdvisor.com/tools/wordpress-plugins/watermark-plugins-for-wordpress/
Video Tutorial: http://mywebsiteadvisor.com/learning/video-tutorials/bulk-watermark-tutorial/
Requirements:
<ul>
<li>PHP v5.0+</li>
<li>WordPress v3.3+</li>
<li>GD extension for PHP</li>
<li>FreeType extension for PHP</li>
</ul>
To-do:

Bulk Watermark

Adds an image and/or text watermark to all uploaded images, using PNG images with transparency.

sverde1

This plugin allows you to watermark your uploaded images. You can create watermark with different fonts, colors and 
apply those watermarks to different image sizes (thumbnail, medium, large, fullsize). You can also position the watermark 
anywhere on the image within Watermark RELOADED settings. Watermarking settings are simple to use and provide you with 
instant preview of how your watermark will look like on the uploaded image.
<a href="http://eappz.eu/en/products/watermark-reloaded-pro/" rel="nofollow ugc">Upgrade to Watermark RELOADED Pro</a> for more 
watermarking features:
<ul>
<li>watermark opacity</li>
<li>image watermark</li>
<li>watermark background color</li>
<li>text watermark with outline</li>
<li>text watermark with variables</li>
<li>upload time option to turn off the watermarking</li>
<li>many more amazing features</li>
</ul>
Requirements:
<ul>
<li>PHP5</li>
<li>GD extension for PHP</li>
<li>FreeType Library</li>
</ul>
To-do:
<ul>
<li>Watermark RELOADED Bug fixing (request by: all)</li>
<li>Don’t display watermark on images where watermark would overflow image (request by: alex)</li>
<li>Watermark aditional image sizes added by other plugins (request by: twincascos)</li>
<li>Watermark images that were uploaded before plugin was installed (request by: anchy-9, Blogging Junction, Ashkir, Mobile Ground, Nicolas)</li>
<li>Image size aware watermark (request by: brohism)</li>
<li>Watermark outside picture</li>
</ul>

Watermark RELOADED

Add watermark to your uploaded images and customize your watermark appearance on a user friendly settings page.

Bulk Watermark vs Watermark RELOADED