I don't think Apple permits this. I think it isn't possible unless you've made a backup of your iPad and restore from the backup, or if you've backed up the app itself with iTunes on your computer.
Actually, I have discussed this at length with Apple. They inform me that when I go to my purchased items area of the app store and re-download a product, I should get an option for the last compatable version. If I do not, according to Apple, it means the developer pulled it. So my question is WHY? Does Adobe realize just how expensive a new iPad is? Why can't the hundreds of thousands of users who CANT upgrade to iOS 10 have the last version that worked for iOS 9.3.5?
Aug 24th... Amendment
I just checked again and low and behold I CAN now download my 9.3.5 version! THANK YOU ADOBE! Thank you for listening and considering all of us 9.3.5 users!