P: Exporting Artboards to PDF are much larger in file size

Thanks. I can reproduce. 

Here is a workaround:

1. Quit Photoshop

2. Back-up these two files which are located in the Photoshop application folder at the following location: 

• Presets/Scripts/ArtBoards To PDF.jsx
• Presets/Scripts/ArtboardExport.inc

3. Download the zip file from here and double-click it to unzip: https://adobe.ly/2kc2snD

4. Place the two files in the same folder as above Presets/Scripts/  (You may be asked to provide your administrator password to replace the files)

5. Restart Photoshop