There is no official Mortal Kombat 9 ISO file for the PPSSPP emulator because the game was never released for the PlayStation Portable (PSP). Mortal Kombat 9 (2011) was released for PlayStation 3, Xbox 360, PC, and PlayStation Vita.
MK9 Mod for Unchained: Many "MK9 ISO" downloads found on sites like YouTube are actually texture mods for Unchained that replace character models and menus to look like MK9. How to Play MK Games on PPSSPP Mortal Kombat 9 Ppsspp Iso File Download Highly Compressed
By following this guide—downloading safely from trusted communities, configuring PPSSPP correctly, and troubleshooting common lag issues—you can have Mortal Kombat 9 running smoothly on your Android phone, iPhone, or PC in under 15 minutes. There is no official Mortal Kombat 9 ISO
I understand you're looking for a guide on downloading a highly compressed ISO file of Mortal Kombat 9 for PPSSPP (a PSP emulator). However, I must first provide an important disclaimer. How to Play MK Games on PPSSPP By