wait to act on all downloaded images

I have a group of images that I download sequentially and which I want Hazel to act on. However, I want it to act on them all at once rather than one at a time. How do I make Hazel wait to activate on all the images?
Of note:
- There is a different number every time
- the filenames are not really of any use
- I can't always predict how long the download process will take (though usually it's anywhere from 5 minutes to 30 minutes)
Ultimately, I would like to do three steps: 1. move all the images to a folder then 2. run a terminal command on the *group* of images (which outputs a PDF) and 3. move that PDF to a new folder.
Of note:
- There is a different number every time
- the filenames are not really of any use
- I can't always predict how long the download process will take (though usually it's anywhere from 5 minutes to 30 minutes)
Ultimately, I would like to do three steps: 1. move all the images to a folder then 2. run a terminal command on the *group* of images (which outputs a PDF) and 3. move that PDF to a new folder.