I'm using an old computer (2015 MacBookPro running Mac OS 11.5.2) to test and tried the ConvertToPDF.workflow from @Athena, giving permissions... It produced a blank pdf.
I then tried to follow the directions of @ccstone with this workflow, but there is no "Save As..." in Automator. So, I chose "Export..." which seemed the same, gave it a different name and saved. Again, I got a blank pdf.
Therefore, didn't get around to trying the KM macro from @Athena. Literally had to catch a train so had to leave after that...
@Athena I was using .png, but because of your note I just converted those to .jpg and tried it again. The workflow worked. I'll work on this more when I have a chance.
@Tony That's weird. The workflow works fine for me with .png or .jpg. Anyway, see if this helps: I'm attaching the workflow with image conversion to .jpg prior to combining into a PDF. LMK? Convert to PDF JPG Conversion.workflow.zip (120.0 KB)