When you delete a document from your iOS device, the file in question can still be recovered and accessed by other people. One way to permanently remove files from your iOS gadget is to use a program like iMyfone Umate Pro.
This tool might also come in handy if you want to sell your iOS device and you need to delete all of its data, without leaving any traces behind.
iMyfone Umate Pro is compatible with various iOS device models, enables you to erase multiple types of files from the connected gadget, and allows you to preview your iOS data before permanently deleting it from your iPhone, iPad or iPod.
Two things bother me about this program: needs iTunes to be installed on your PC in order to function and the fact that it might take a while to complete the scanning processes. In my testing, the utility didn't recognize my iPhone until I installed iTunes on my computer. Furthermore, it took a while to look for iOS temporary files and large documents.
In my opinion, you should first test the trial version of the tool, see how it works on your computer, and then decide if it's worth buying it or not.