I think this is a dumb question, so bear with me...

Say I am importing a map that is 100 PPI and 30 inches by 30 inches

I want to increase resolution (for printing) to 300 PPI without resampling

If I increase the resolution in Photoshop to 300 PPI, the image size decreases to 10 inches by 10 inches, right? So have I successfully created a 300 PPI image, albeit one 1/3 the size?