You can download the schematic for the RS-232 development board from the Digi web site. That has the circuitry you need, and to the best of my belief Digi are happy for people to make use of it.
I'm sure you could find ways other than MAX232, though that seems to be the convenient solution that most people go for.
Your first post mentions that the PC requires 5V data input. I'm assuming that it's a standard PC with RS-232 levels. If it really does want 5V, then a different level shifting circuit would be needed.