Renaming every multiple of 9?

After some work I managed to get an image editor to clip all the player card images from a pdf I have, but now the files are not showing the cards in sequential order. I determined that I need to renumber all nine of the first 9 cards and every multiple of those original card numbers. For example, I have the card numbered 9 that needs to be numbered 1, but 18, 27, 36, etc. all need to be reduced by 8 as well. in order to put them in the sequential order I want to have them displayed in when I sort them by name, but I can not figure out how to do it and it's driving me nuts!