It's easy to Google Windows 8 password recovery tools. However, the PC I'm working on right now doesn't support legacy boot and can only boot from GPT partitioned USB sticks. I'm using Rufus for creating my bootable stick, but to boot in UEFI mode I have to burn a UEFI bootable ISO onto the stick. I can't find a UEFI bootable ISO around. Is there a sort of converter from normal ISO to a UEFI bootable one?
Which ISO are you trying to boot in UEFI? Check if it has a file
/boot/bootx64.efi or the like. If it does, then just follow @Snayob's comment.
A non-UEFI bootable ISO CAN be made into a UEFI bootable USB stick if it has the UEFI bootloader as a file. The presence of a file like this cannot however boot the CD/DVD itself because CD/DVD booting requires more than just a file. Not so for USB sticks.