I am trying to edit and create a new dynamic desktop file. I've tried to create a new file by using Preview. I'd open the images I want to use, select them all, and print them as a PDF file. I then would open the PDF file and export it as a HEIC file. I believe by saving the images as a PDF file all of the individual image information is lost. Preview creates essentially a flat HEIC file when it saves the PDF file as a HEIC file. Preview will not save the images as a single file any other way as far as I know. Is there a way to do this in Preview or do I need to use another app?