Denice: but is there a way to edit what is exported permanently so I don't have to do that every day?
Not exactly - the only way to acheive this without editing your grid would be to build a custom report using the report designer. While possible, it's certainly more customization than adding an export to pdf action.
Here's an option that might work (depending on your needs). You could hide the fields by default that you're hiding now so your export only contains the columns you want. To see those additional columns you'll need to use the same process used for printing to hide/unhide columns. It's six of one and half a dozen of the other, do you want to hide before or unhide after?
If you want to hide before, while editing your grid columns on step 2, click the advanced link and then check Hidden when screen first loads? This will keep the field hidden until you click the gear icon to unhide it.
~C