Below are the step-by-step instructions on how to increase the text size in Opera 8 / 9 for OS X
In Opera can increase the size of images as well as text.
You can quickly increase or decrease the size of both text and graphics using the numberpad ' + ' (or ' 0 ' ) and ' - ' (or ' 9 ' ) keys. Each press will increase or decrease the size by 10%. However these changes will not be remembered next time you open Opera.

Fig 1
Fig 2
Note: If this does not work it could be because your computer settings cannot be changed due to local IT policies - contact your local IT support for further help.