Adobe Lightroom has a feature called Smart Previews. Smart Previews, in the most basic sense, are small DNG copies of the original RAW files. 

These copies (Smart Previews) allow images to be edited in Lightroom's Develop module, even when the RAW files are on another hard drive. 

When sending Prime Edits your Lightroom catalog, you need to Build Smart Previews. It's really easy.

Step 1: Open your Lightroom Catalog

Step 2: Navigate to Library > Previews > Build Smart Previews

      - This will start the building of your Smart Previews file, and a status bar will appear in the top right-hand corner of your Lightroom Catalog.

      - The Smart Previews file will appear in the same folder where you keep your Lightroom catalog.

Build Smart Previews from The Larken Photo & Video Co. on Vimeo.

If you are wanting to export a catalog from a large catalog, follow these steps:

Step 1: Select the files you want to send to Prime Edits

Step 2: Navigate to File > Export as Catalog...

Step 3: Name your catalog, select the export destination, select "Build and Include Smart Previews"

Step 4: Click "Export Catalog"