On this video by photographer Anthony Morganti explains how to add a watermark to an image in Adobe Lightroom.
Morganti shows how to create both a text watermark and a graphic watermark and modify both of them. If you are going with text you will need to choose the font and the style (pretty tedious process). You can add shadows, effects, change size and more.
Next Morganti looks at adding a watermark in the form of an image (PNG with transparent background should work well). Finally Morganti shows how to export the finished image.
We have looked at different ways to create a watermark in both Photoshop and Lightroom (some more in depth than this video), Aaron Nace did a video on adding a watermark in Photoshop entitled “The Best Way to Watermark Your Images in Photoshop“, we also looked at “Creating Watermarks in Lightroom 5” by Mark Wallace, a different look at the same thing on “How to Add a Watermark in Lightroom 5” with Howard Pinsky and “Creating a Watermark in Photoshop – A Quick Tutorial” by Jen Swedhin.