Do I need any antivirus software with the Linux/Unix systems?
Assuming you're only installing from official repositories, then no.
Packages found out in the wild, and coming from non-officially maintained repos might be another story, exercise proper due-dilligence when installing from these sources. -- Support Bacteria -- It's the Only Culture Some People Have
you'll have to get the Adobe stuff outside of the standard repos... although there are open source alternatives to Adobe reader, which are bundled with most distros so unless you need it for a specific reason that only leaves Flash. -- Support Bacteria -- It's the Only Culture Some People Have