If you still have a CS3 retail serial from an original disc, you can install it legally. But Adobe deactivated many old activation servers; you might need to contact support. No “portable” version is legal.
It looks like your request covers two very different areas: a specific software version and a request for essay writing adobe illustrator portable cs3 mediafire
. Using extremely old software can lead to file corruption when trying to open modern Recommended Alternatives If you still have a CS3 retail serial
"Portable" versions are typically unauthorized re-packs designed to run without a full system installation. Adobe CS3 and Windows 10 [CS3 is dead] | Community It looks like your request covers two very
Would you like help getting started with a legal, free alternative like Inkscape instead?
: Enhanced compatibility with other CS3 apps like Photoshop and Flash. Modern Alternatives
: One of the first versions optimized for both Intel-based and PowerPC-based Macs (Universal Binary) and Windows Vista. System Requirements (Classic Desktop)