It might have been clearer if you'd shown the whole dialog...
What are you really trying to accomplish? Your attempt to "change the media size" confuses me.
Bottom line is this: If you set the image size via the Image - Image Size dialog, then that's how big it will print (assuming it all fits and you haven't checked the Scale to Fit Media box and have set the scale factor to 100%).
It's inside the printer driver settings (available via the [Print Settings...] button) where you set the paper size.
As Noel said it would be more helpful to see the entire dialog box. Also what printer are you using? The dialog boxes change in photoshop based on the different manufacturer printer driver. So it's hard to give advise.
Sounds like you have a small document say, 4"x5" and you want to print it centered ( I presume ) on a 8.5x11 sheet of paper.
Again, as Noel said, you would pick the paper size in your printers print dialog box. The document should not change size.
< , but not sure what happens when i change it >
It will change the size of the image that is printed on the paper. But the paper size selected stays the same.
Thanks. I think it's just an instance of trying to change settings in the wrong place. I was just trying to center a smaller image on a larger piece of paper (media). And just to answer your question about the printer I was using; I am using a xerox 700 digital press. I was trying to make up for the lack of a bleed on a file that a customer had submitted to me without making any changes in my creo rip software.
In the original posting above, CoGordo4 asks how to UNLINK the scale, height and width options in that print window. I'd also like to know if that is possible. I don't always want my piece to scale proportionally. Thanks.