Whatever you set the report margins to in design view will be the settings for who ever uses the report.
If you set the margins to .5" then save the changes, then open the report in design view on your user's PC, you should find the margins at .5". You're not changing margins on a PC or a printer, your changing margins on the individual report so who ever uses the report will use the margins on that report.
Now, if you allow your users to open reports in design view and change margins, well then all bets are off and the report will then print according to what the new report margins are set to.
Good Luck.