Truefy

<a href="https://embed.truefy.ai/" rel="nofollow ugc">Truefy Embed</a> allows you to invisibly watermark images uploaded to the WordPress Media Library or a WordPress Post. 
The Plugin will also directly sync the changes in Image Caption from WordPress to Truefy Embed 
Once uploaded, you can view them in the Image library in Truefy Embed Website, where you can add or edit the critical details like Image Capture Datetime, Publisher Details etc.
For more information, check out <a href="https://embed.truefy.ai/integrations/wordpress" rel="nofollow ugc">plugin page</a> or email us at support@truefy.ai
You can check Truefy Embed’s Terms of Service at <a href="https://embed.truefy.ai/legal/tos" rel="nofollow ugc">ToS Page</a>
<h4>Features include:</h4>
<ul>
<li>Auto Invisible Watermarking – Images uploaded to Media Library or a Post can be automatically invisibly watermarked</li>
<li>Manual Invisible Watermarking/De-Watermarking – Images can be manually watermarked, and even be de-watermarked</li>
<li>Image Caption Syncing – Captions added for Images in Media Library or Post Caption, are directly synced to Truefy Embed Servers</li>
</ul>

Truefy Embed

Truefy Embed's proprietary AI invisible watermarking technology secures your images by allowing you to add critical details directly into the pix …

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.

Truefy Embed vs Bulk Watermark