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Adobe Photoshop should not be needed in order to open and install any printer firmware update.
Check your printer manufacturer's website for instructions about how to update the firmware on your printer.
Program and operating system updates, including firmware updates, I've encountered are usually packaged as a self-installing program, often with the filename and extension of '.dmg' ("disk Image" for a computer running Mac OS X), or perhaps a '.zip' file (a method of encoding and shrinking several files into a single smaller file, often used for Windows computers, but occasionally for Mac.)
It's possible that the update you've downloaded is intended for installation from a Windows computer instead of from a Macintosh computer.
If you use the printer wirelessly, it's also possible that your computer needs to be directly connected to the printer via a USB cable in order to install a firmware update. Again, check the computer manufacturer's firmware update instructions.
Message was edited by: kostby