If you are an original owner and need to document your license, you can try these methods: Illustrator [CS3 is dead and gone] - Adobe Community
Adobe Illustrator CS3 is a legacy software released in March 2007 Adobe Illustrator Cs3 Serial Number
: For a short period after the server shutdown, Adobe provided a special "activation-free" installer and a new replacement serial number to registered owners. However, Adobe removed these links and ended this replacement program in late 2019/early 2020 Official Support Status If you are an original owner and need