This AppleScript automates the process of placing a multiple paged PDF into some pre existing image frames. It can also be used to drop a folder of files into selected image frames. If there are more pages in the PDF (or images in the folder) than there are selected image frames, you have the option to let the script duplicate the current Indesign page until all the PDF pages or images have been placed.
Note the script tries to identify the grid and places images or pages from the top left box and continues row-by-row down to the bottom right. It can even cope with the images being a little bit staggered.
Anything that is not an image frame gets ignored as you can see with the two heading text frames that were also selected. Any selected grouped items will also be ignored.
Check out this video demonstration to see it in action.
If you choose to place a multi paged PDF into only the selected pages (not duplicate), the script will ask you to select a starting page. Then if you try placing the same PDF again, it will remember the page where it finished last time and continue from the next page.
This is an AppleScript so it only works on a Mac.